Towing capacity is the heaviest loaded trailer that a car’s manufacturer rates it to tow. But it is only one of several limits. Understanding towing capacity means checking the gross train weight, the car’s own maximum authorised mass, the noseweight and, for trailers without brakes, the 750 kg rule. The physics of mass, force and kinetic energy explains why every one of those limits exists. This guide uses UK rules checked in October 2026 and includes a weight checker, calculators and a quiz.
What is towing capacity?
Towing capacity is the maximum mass of loaded trailer that your car is rated to pull. Most cars have two figures: a higher one for a braked trailer (one with its own brakes) and a lower one for an unbraked trailer. GOV.UK says that most cars have a maximum weight they can tow, usually listed in the handbook or specification sheet.
The key word is “loaded”. A caravan that weighs 1,200 kg empty can weigh far more once it is full of bedding, gas bottles, food and water. The limit applies to what is actually on the road behind you, not to the figure in the brochure.
If the handbook is not to hand, look for the VIN plate. GOV.UK says it is normally under the bonnet or inside the driver’s door. It may list a gross train weight, which is the weight of the fully loaded car plus the fully loaded trailer, and which must not be exceeded. GOV.UK also says that if your VIN plate does not list a train weight, you should not use your vehicle for towing.
You may meet American terms online. GVWR (gross vehicle weight rating) is roughly the same idea as a car’s maximum authorised mass, and GCWR (gross combined weight rating) is roughly the gross train weight. This article uses the British terms, which are the ones on UK plates and in UK handbooks.
The rules described here apply to Great Britain. Northern Ireland has its own licensing rules, so check nidirect if you live there.
The physics of towing: forces on a car and trailer
A towing limit is not an arbitrary number. It comes from the forces acting on the car and trailer as they move, and from how much energy the brakes have to remove when you stop. The same ideas appear in GCSE Physics, so the explanations below double as revision.
Four kinds of force matter. The engine provides a driving force through the wheels. Resistive forces, mainly air resistance and rolling friction, act backwards, and air resistance grows with speed. Gravity pulls everything down as weight, and the road pushes up with a normal reaction on every wheel.
Mass and weight
Mass is the amount of matter in an object and is measured in kilograms. Weight is the force of gravity on that mass and is measured in newtons. You calculate it like this:
W = m × g
On Earth, g is 9.8 N/kg. A loaded trailer of 1,500 kg therefore weighs 1,500 × 9.8 = 14,700 N. Plates and handbooks quote masses in kilograms, even though people say “weight” in everyday speech. Our guide to common comparisons in physics sets mass against weight, and scalars against vectors, side by side.
Driving force, resistive forces and F = ma
When a car and trailer move at a steady speed, the driving force equals the resistive forces. The forces are balanced, so there is no change in speed. That is Newton’s first law, which we explain in more detail in Newton’s laws of motion.
If the driving force is bigger than the resistive forces, there is a resultant force and the outfit accelerates. Newton’s second law links the three quantities:
F = m × a
Take a car and caravan with a total mass of 2,900 kg. The engine gives a driving force of 3,000 N and the resistive forces total 1,550 N. The resultant force is 3,000 − 1,550 = 1,450 N, so the acceleration is 1,450 ÷ 2,900 = 0.5 m/s². The same resultant force on the 1,600 kg car alone would give about 0.91 m/s². More mass means less acceleration, which is why an outfit feels slow when you pull away or overtake.
Try your own numbers in the calculator.
Why hills make towing harder
On a slope, part of the weight acts down the hill. On a 10% gradient, which rises 1 m for every 10 m along the road, that is about one-tenth of the weight. For a 2,900 kg outfit it comes to about 2,800 N, and the engine has to supply this extra force on top of the resistive forces.
Going downhill, the same force works in your favour, which is dangerous if you are not ready for it. The brakes must hold back that extra push. In energy terms, the gravitational potential energy store of the outfit is being transferred to its kinetic energy store, a change you can read about in the different kinds of energy and their uses.
A loaded trailer has a mass of 1,200 kg. Calculate its weight. (g = 9.8 N/kg) (2 marks)
W = m × g = 1,200 × 9.8 = 11,760 N.
Towing capacity and the other UK weight limits
Meeting the towing capacity does not mean every other weight limit has been met. A safe, legal outfit has to stay under several limits at once, and the lowest limit wins. The infographic below shows the five you will meet most often, with example figures for learning only.
Kerbweight, MAM and payload
Kerbweight is the mass of the car ready to drive, with fuel, fluids, tools and spare wheel. The European definition includes a 75 kg driver, but some manufacturers leave that allowance out, so check how your handbook defines it.
MAM stands for maximum authorised mass. It is the most a vehicle or trailer may weigh when loaded, and GOV.UK says it is normally shown on a plate or sticker on the vehicle or trailer. For caravans the same idea is called MTPLM, the maximum technically permissible laden mass.
Payload is the MAM minus the kerbweight. It is the extra mass the car can carry: passengers, luggage and accessories. As we will see, the noseweight pushes down on the towbar, so it uses up part of that payload too.
| Term | What it means | Where to find it |
|---|---|---|
| Kerbweight | Car ready to drive, with fuel and fluids | Handbook or specification sheet |
| MAM (car) | Most the loaded car may weigh on its own | VIN plate, handbook |
| Payload | MAM minus kerbweight: what the car can carry | Work it out from the two figures |
| Towing capacity | Heaviest loaded trailer the car is rated to tow (braked and unbraked figures) | Handbook or specification sheet |
| Gross train weight | Loaded car plus loaded trailer | VIN plate (second weight) |
| MTPLM (caravan) | Most the loaded caravan may weigh | Plate on the caravan |
| MiRO (caravan) | Mass in running order: ready for the road, without personal effects | Caravan paperwork |
| Noseweight | Downward load of the trailer on the towball | Towball limit in the handbook |
Gross train weight
The manufacturer’s plate shows four weights. The first is the maximum weight of the car on its own. The second is the maximum weight of the car and trailer combined, which is the gross train weight. The third and fourth are the maximum front-axle and rear-axle weights. GOV.UK points out that these maximums include passengers, other loads and fuel.
For a braked trailer, the car and the loaded trailer together must not weigh more than that second figure on the plate. This is why a fully loaded family car can tow less than the headline number in the brochure.
Noseweight (towball load)
Noseweight is the downward force that the trailer’s coupling puts on the car’s towball. Too little, and the trailer can become unstable. Too much, and you overload the towball and the rear axle. Your handbook gives the towball limit.
The Caravan and Motorhome Club recommends a noseweight of approximately 5–7% of the caravan’s actual laden weight, which is generally between 50 and 90 kg. The Camping and Caravanning Club advises making it as heavy as possible without exceeding the car’s towball limit, and says towball and caravan noseweight limits are typically about 50–100 kg. Both are guidance from clubs, not law, and your own car’s towball limit always comes first.
How to work out how much your car can tow
If you have ever asked “how much can my car tow?”, the honest answer is “it depends on how full it is”. Here is the method, using the example in the infographic.
- Find the towing limit in the handbook for your trailer type, braked or unbraked.
- Find the gross train weight, the second weight on the VIN plate.
- Work out the real mass of your loaded car, including people, luggage, fuel and the noseweight.
- Subtract: train weight minus loaded car gives the allowance for the trailer.
- Your loaded trailer must stay under the lowest of these limits, and under 750 kg if it has no brakes.
In the example, the train weight is 3,800 kg and the loaded car is 2,250 kg. That leaves 3,800 − 2,250 = 1,550 kg. The handbook towing capacity is 1,800 kg, but the lower figure wins. A loaded trailer of 1,600 kg is therefore 50 kg over the limit, even though it is below the headline towing capacity.
Now try it with your own figures. This is a learning tool only: always use the numbers on your own car’s plate and handbook.
Electric cars have towing figures too, and they are listed in the handbook just like petrol and diesel models. Some models may not be approved for towing at all, so check before you buy a trailer. Our guide to how electric cars work explains the technology behind them.
The 85% guideline
Both big UK caravan clubs give a rule of thumb for matching a car and caravan. The Caravan and Motorhome Club says to aim for a towed load of around 85% of the car’s kerbweight. The Camping and Caravanning Club recommends 85% or less, and adds that experienced towers may go up to 100%.
This is a stability guideline for new towers, not a legal limit. The legal limits are the figures on your plate and in your handbook, plus the GOV.UK rules covered later in this article.
Towing is a good example of physics in everyday life: masses, forces and energy decide what is safe. People tow far more than caravans, so here are three common loads.
Each of these has its own plate with its own maximum mass. The car’s limits and the trailer’s limits both have to be respected, and the smaller number wins.
Braked vs unbraked trailers
Trailers come in two kinds. A braked trailer has its own brakes. An unbraked trailer relies entirely on the car to stop. GOV.UK says a trailer must have a working brake system if it weighs over 750 kg when loaded, and that some smaller trailers have brakes too, but these are optional.
For an unbraked trailer, GOV.UK sets two limits. The loaded trailer must not weigh over 750 kg, and it should not weigh more than 50% of your car’s weight. The rule of 750 kg is a maximum, so a light car may be limited to far less.
By law you must also use a breakaway cable or secondary coupling. It engages the trailer’s brakes, if fitted, or stops the trailer if it becomes detached from the car. The cable must not be worn, needs enough slack, and must not drag on the ground. The Highway Code says the trailer must have a secondary coupling device, such as a safety chain.
Why does the difference matter? Think about energy. With no trailer brakes, the car’s brakes must remove the kinetic energy of the trailer as well as their own.
Stopping works through friction between the brake pads and the discs, and between the tyres and the road. Friction transfers kinetic energy into heat, which is why brakes get hot. Our article on the disadvantages of friction explains the wear and overheating that follow.
Loading, noseweight and snaking
How you load a trailer affects how it behaves. The Highway Code says to distribute weight evenly, with heavy items over the axle or axles, and to make sure there is a downward load on the tow ball. It adds that doing so should minimise the possibility of swerving or snaking and loss of control. You also must not exceed the manufacturer’s recommended weight and tow ball load, and the load must be secure and must not stick out dangerously.
The physics is about the centre of mass, the point where the mass of the trailer seems to act. If a heavy load sits at the back, or the noseweight is too low, the centre of mass moves behind the axle and the trailer becomes less stable. Speed and side gusts make it worse. Heavy items kept low and over the axle keep the centre of mass low and central.
Loading rules of thumb
- Put heavy items low and close to the axle, as the Camping and Caravanning Club advises.
- Spread the load evenly from side to side and keep it secured.
- Never exceed the trailer’s maximum mass, the car’s towball limit or the manufacturer’s recommended noseweight.
- Do not stack heavy kit at the back, behind the axle.
- Re-check the load and noseweight after any change, such as a full water tank.
What to do if the trailer starts to snake
Snaking, also called sway, is when the trailer swings from side to side behind the car. GOV.UK gives clear advice: ease off the accelerator and reduce your speed gently. It is a sign that either you are going too fast or the trailer is loaded incorrectly.
Do not brake harshly on a bend. The Highway Code gives the same warning. When you are safely able to stop, check the load and noseweight before you set off again.
Mass, speed and stopping distance
Now for the part of towing physics that matters most for safety. A moving object has energy in its kinetic store, given by:
Eₖ = ½ × m × v²
Momentum is a separate idea. It is the product of mass and velocity:
p = m × v
Speeds on UK roads are in miles per hour, so convert first. 1 mph is about 0.447 m/s, which makes 50 mph about 22.4 m/s. A car and caravan of 2,900 kg at that speed has about 724 kJ of kinetic energy. The 1,600 kg car on its own has about 400 kJ, so the outfit has roughly 1.8 times as much. At 60 mph, the outfit has about 1,043 kJ. Its momentum at 50 mph is about 65,000 kg m/s, compared with about 36,000 kg m/s for the car alone.
Because speed is squared, doubling speed gives four times the kinetic energy. Doubling the mass only doubles it. Higher speed means much more energy for the brakes to remove, which is one reason lower speed limits apply when towing.
To stop, the brakes do work against the motion. Work done is braking force times braking distance, and it must equal the kinetic energy removed. With the same braking force, more energy means a longer braking distance. Braking distance is roughly proportional to v².
The Highway Code gives typical stopping distances for a car on a dry road in good conditions. They are split into thinking distance and braking distance:
| Speed | Thinking distance | Braking distance | Total stopping distance |
|---|---|---|---|
| 30 mph | 9 m | 14 m | 23 m |
| 50 mph | 15 m | 38 m | 53 m |
| 60 mph | 18 m | 55 m | 73 m |
| 70 mph | 21 m | 75 m | 96 m |
These figures are for a car on its own. Towing adds to them, and the Highway Code warns that stopping distance may increase significantly when towing. Our guide to motor vehicle collisions and road safety looks at how speed affects what happens in a crash.
Explain why doubling the speed of a car and caravan more than doubles its braking distance. (3 marks)
Kinetic energy = ½mv², so doubling the speed gives four times the kinetic energy. The brakes must do work (force × distance) equal to that energy. With the same braking force, the braking distance is about four times longer.
UK towing rules in 2026: licence, speed and equipment
Weight limits are only part of the picture. You also need the right licence, a legal speed and the right equipment. These notes cover Great Britain and were checked against GOV.UK in October 2026. They are a guide, not legal advice, so always check the current GOV.UK pages before you tow.
What can I tow on my licence?
The rules changed on 16 December 2021. Drivers in Great Britain who passed their car test from 1 January 1997 can now tow trailers up to 3,500 kg MAM without taking an extra car-and-trailer test. The separate car-and-trailer (B+E) test stopped from 20 September 2021. GOV.UK says category BE will be added to your licence the next time DVLA issues a new photocard.
If you passed your test before 1 January 1997, you can usually drive a vehicle and trailer with a combined weight of up to 8,250 kg MAM. Heavier combinations need a C1+E entitlement, up to 12,000 kg MAM combined.
Northern Ireland has its own licensing rules, so check nidirect rather than relying on this section. A licence that lets you tow a trailer does not override your car’s own limits: you still need to stay within its towing capacity and train weight.
Speed limits when towing
A car towing a caravan or trailer has lower speed limits than a car on its own. A limit is a maximum, not a target, and conditions may make a lower speed safer.
| Road | Car | Car towing a caravan or trailer |
|---|---|---|
| Built-up areas | 30 mph (20 mph in Wales) | Same |
| Single carriageway | 60 mph | 50 mph |
| Dual carriageway | 70 mph | 60 mph |
| Motorway | 70 mph | 60 mph |
You must also not drive in the right-hand lane of a motorway with three or more lanes when towing.
Equipment the law requires
- Tow bar: it must be type approved, with a label showing its approval number. This is not needed if the car was first used before 1 August 1998.
- Towing mirrors: you must have an adequate view behind. Fit towing mirrors if the trailer is wider than the rear of the car. The fine is up to £1,000 and 3 penalty points.
- Number plate: the trailer must show the same number plate as the towing car.
- Lights and brakes: working lights, and working brakes on any trailer weighing over 750 kg when loaded.
- Breakaway cable or secondary coupling: it must be used and correctly attached.
- Size: maximum trailer width is 2.55 m. If the towing vehicle’s MAM is 3,500 kg or less, the trailer must not be longer than 7 m, not counting the A-frame.
- Tyres: no cuts or bulges, inflated for the load, and tread of at least 1.6 mm across the central three-quarters of the tread and around the whole circumference.
Before you tow: a safety checklist
GOV.UK publishes safety checks for towing a trailer or caravan with a car. Use them before every trip, not only the first. The infographic shows seven of them, and the checklist below has eight. Tick each one as you go; your ticks are remembered in your browser.
- I have checked the towing limit, train weight and towball limit in the handbook.
- I have weighed or estimated the loaded trailer and the loaded car.
- Heavy items are low, over the axle and secured.
- Tyres on the car and trailer are correctly inflated for the load, with at least 1.6 mm of tread and no cuts or bulges.
- The coupling is locked on the towball and at the correct height.
- The breakaway cable is attached, with enough slack, and is not dragging.
- All trailer lights, indicators and brake lights work.
- Towing mirrors are fitted and adjusted.
For trailers up to 3,500 kg, the National Trailer and Towing Association (NTTA) offers a free safety check, and training is available through schemes such as the Safe Towing Scheme. Safe towing is a good example of why road safety matters for every driver. This article is not legal advice: use your own car’s plate and handbook, and the current GOV.UK guidance.
Frequently asked questions about towing capacity
What does towing capacity mean?
Towing capacity is the maximum mass of loaded trailer that the manufacturer says a car can tow. Most cars have a higher figure for braked trailers and a lower one for unbraked trailers. You can usually find it in the handbook or specification sheet. It is only one of several limits to check.
How do I work out how much my car can tow?
Find the towing limit for your trailer type and the gross train weight on the VIN plate. Subtract the real weight of your loaded car from the train weight. Your loaded trailer must be under the lowest of those figures, and under 750 kg if it has no brakes.
What is gross train weight?
Gross train weight is the weight of the fully loaded car plus the fully loaded trailer, and it must not be exceeded. It is normally listed on the VIN plate as the second weight. If your VIN plate does not list a train weight, GOV.UK says you should not use the vehicle for towing.
What is the maximum weight of an unbraked trailer in the UK?
A loaded unbraked trailer must not weigh over 750 kg, and GOV.UK advises that it should not weigh more than 50% of your car’s weight. Trailers that weigh over 750 kg when loaded must have a working brake system. Always check your own car’s handbook as well.
What is the 85% rule for towing a caravan?
The 85% rule is a guideline from UK caravan clubs. They advise matching a caravan to about 85% of the car’s kerbweight, with experienced towers sometimes going up to 100%. It is about stability, not law. The legal limits are the figures on your car’s plate and handbook.
What should the noseweight of a caravan be?
The Caravan and Motorhome Club recommends about 5–7% of the caravan’s actual laden weight, generally between 50 and 90 kg. The Camping and Caravanning Club says towball limits are typically about 50–100 kg. Never exceed your car’s own towball limit, which is in the handbook.
Can I tow a caravan on a standard car licence?
In Great Britain, if you passed your car test from 1 January 1997, you can tow trailers up to 3,500 kg MAM. Earlier drivers can usually drive a vehicle and trailer up to 8,250 kg MAM combined. Your car’s own limits still apply. Northern Ireland has separate rules, so check nidirect.
What is the speed limit when towing in the UK?
For a car towing a caravan or trailer in Great Britain, the limit is 50 mph on single carriageways, and 60 mph on dual carriageways and motorways. In built-up areas the usual limit applies. These are maximums, and you must not use the right-hand lane of a motorway with three or more lanes.
What should I do if my caravan starts snaking?
Ease off the accelerator and reduce your speed gently. GOV.UK says snaking is a sign that you are going too fast or the trailer is loaded incorrectly. Do not brake harshly on a bend. When it is safe to stop, check the load and the noseweight.
Why does towing increase stopping distance?
A car and trailer have more mass, so they have more kinetic energy at the same speed. The brakes must remove all of it, which takes a longer distance. The Highway Code says that stopping distance may increase significantly when towing, especially if the trailer has no brakes of its own.
