Towing Capacity and Payload Calculator
Enter the vehicle weights from the plate, what you are towing and what you are carrying. This checks the outfit against both limits at once.
Payload left
300kg
- Payload available
- 850 kg
- Left after loading
- 300 kg
- Tow-ball download
- 250 kg
- Vehicle and trailer together
- 5,250 kg
- Inside both limits, with 300 kg of payload to spare.
- Two limits apply at once and people usually check only the first. Gross vehicle mass caps the vehicle itself; gross combination mass caps the vehicle and trailer together.
- Everything counts: passengers, luggage, a full tank, roof bars, a tow bar and anything bolted on since. Kerb weight is the vehicle empty.
- Too little download makes a trailer sway and too much overloads the rear axle. Around a tenth of the trailer weight is the usual target, but check what the vehicle and the hitch are rated for.
About towing limits
Two limits apply to a towing setup and people habitually check only the first. Gross vehicle mass caps what the vehicle itself may weigh, fully loaded. Gross combination mass caps the vehicle and trailer together. A trailer comfortably within its own rating can still put the outfit over the combination limit.
The detail that causes most of the trouble is where the tow-ball download goes. The trailer rests part of its weight on the vehicle's hitch, and that weight counts against the vehicle's payload — not the trailer's. On a 2,500kg trailer with a ten per cent download, 250kg lands on the vehicle before a single passenger gets in.
Payload disappears faster than people expect once it is counted honestly. Kerb weight is the vehicle empty; everything after that comes out of the payload, including passengers, luggage, a full tank, roof bars, the tow bar itself and anything fitted since the vehicle was built.
The download figure itself is a balance rather than a target to minimise. Too little and the trailer will sway, which is genuinely dangerous at speed; too much and the rear axle is overloaded and the steering goes light. Around a tenth of the trailer weight is the usual aim, but the vehicle and the hitch each have their own rating and both need checking.
What it works out
- Payload available and payload left
- The tow-ball download, counted against the vehicle
- Gross vehicle mass and gross combination mass together
- Whether the outfit is legal on both counts
The formula
Payload = GVM − Kerb Left = Payload − (Load + Download) Combined = Kerb + Load + Download + Trailer
A vehicle with a 2,200kg kerb weight rated to 3,050kg has 850kg of payload to play with.
The trailer takes the first bite. At a ten per cent download, a 2,500kg trailer puts 250kg onto the hitch, and that lands on the vehicle. Add 300kg of people and luggage and 550kg of the 850 is gone, leaving 300kg.
The combination check is separate. Vehicle, load, download and trailer together come to 5,250kg against a 6,000kg limit, so this outfit is inside both — but only just, and adding a roof box and a full tank would start to matter.
The case to watch for is passing one check and failing the other. A heavier trailer at the same download percentage eats payload from the vehicle and combined mass at the same time, so both limits close in together, and it is entirely possible to be within a vehicle's quoted towing capacity and still be illegal on gross combination mass.
- Kerb weight
- The vehicle empty. Everything you add comes out of the payload.
- GVM
- Gross vehicle mass — the most the vehicle alone may weigh, from the plate.
- GCM
- Gross combination mass — the most the vehicle and trailer may weigh together.
- Download
- The weight the trailer rests on the tow ball. It counts against the vehicle, not the trailer.
A worked example
A 2,200kg vehicle rated at 3,050kg alone and 6,000kg combined, towing a 2,500kg trailer with 300kg of people and luggage.
That works out to 300 kg.
- Payload available
- 850 kg
- Left after loading
- 300 kg
- Tow-ball download
- 250 kg
- Vehicle and trailer together
- 5,250 kg
Questions
How do I work out what I can tow?
Check both limits. Subtract the kerb weight from the gross vehicle mass to get the payload, take off passengers, luggage and the tow-ball download, and separately check that the vehicle and trailer together stay under the gross combination mass.
Does the tow-ball weight count against the car or the trailer?
The car. It rests on the vehicle's hitch, so it comes out of the vehicle's payload. A 2,500kg trailer at a ten per cent download puts 250kg on the vehicle before anyone gets in.
What is the difference between GVM and GCM?
Gross vehicle mass is the most the vehicle alone may weigh. Gross combination mass is the most the vehicle and trailer may weigh together. Both apply at the same time and passing one does not mean passing the other.
Can I be within my towing capacity and still be overloaded?
Yes, and it is common. A trailer within the vehicle's quoted towing capacity can still put the combination over the gross combination mass, particularly with a full car and a loaded trailer.
What tow-ball download should I aim for?
Around ten per cent of the trailer weight is the usual guidance, though the vehicle and hitch ratings take precedence. Too little causes sway; too much overloads the rear axle and lightens the steering.
What counts towards payload?
Everything added to the empty vehicle: passengers, luggage, a full tank, roof bars, a tow bar, and any accessory fitted after it left the factory. Kerb weight is the vehicle bare.
Where do I find these weights?
On the compliance plate, usually inside a door frame or under the bonnet, and in the handbook. Do not use figures from a brochure for a different trim level, since kerb weight varies with specification.
Why does trailer sway happen?
Usually too little download or a load placed too far back, which lets the trailer pivot around its axle. It builds with speed and is very difficult to recover from, which is why the download figure matters more than it looks.