What this calculator works out
This calculator subtracts people, luggage, water and equipment from the vehicle's maximum payload, showing what capacity remains.
Motorhome payload is tighter than most owners realise, and water is the item that consumes it fastest — a full 100 litre tank is 100 kg.
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Before you load
- Payload is the difference between the vehicle's maximum authorised mass and its mass in running order. Both figures are on the VIN plate or in the handbook.
- Mass in running order usually includes a driver at a standard 75 kg and a partly filled fuel tank — check what your manufacturer includes.
- Water is 1 kg per litre. Fresh, waste and hot water tanks all count when full.
- Gas bottles, leisure batteries, bike racks, awnings and solar panels are all payload, and fitted accessories reduce it permanently.
Manufacturer payload figures are calculated, not measured, and options fitted at build reduce them. A public weighbridge costs a few pounds and gives the actual figure, loaded as you travel. Many owners discover on a weighbridge that they are close to or over the limit while believing they had ample margin.
How this calculator works
Payload less what is loaded:
Remaining = maximum payload − people and luggage − water and equipmentA negative result means the vehicle is overloaded as configured. Overloading is an offence, invalidates insurance in some circumstances, and materially affects braking and handling.
Worked example: a 600 kg payload
Using the default figures — 600 kg payload, 250 kg of people and luggage, 150 kg of water and equipment:
- Remaining: 200 kg
200 kg sounds generous until it is itemised. Two gas bottles are around 30 kg, a leisure battery 25, a bike rack with two bikes 45, an awning 25, and a full waste tank another 40. That is 165 kg of ordinary equipment, leaving 35 kg — which is less than a fortnight's food and clothing for two. Travelling with a part-filled fresh water tank is how most owners create the margin.
Common mistakes
- Forgetting water weight. It is 1 kg per litre and dominates everything else.
- Not counting fitted accessories. Solar panels, racks and awnings permanently reduce payload.
- Assuming the brochure payload. Options fitted at build reduce it.
- Ignoring axle limits. A vehicle can be within total weight and over on one axle.
- Never weighing it. A weighbridge is the only way to know.
Frequently asked questions
What are the penalties for overloading?
Fines that increase with the degree of overload, and vehicles can be prohibited from continuing until the excess is removed. Insurance can be affected where overloading contributed to an incident. Enforcement uses roadside weighing, and motorhomes are checked at ports and on holiday routes.
Should I travel with full water tanks?
Generally not. A full 100 litre fresh tank is 100 kg of payload that could be filled on arrival at a site with a water supply. Many owners travel with enough for the journey — 20 to 30 litres — and fill up at the destination. Waste tanks should be emptied before travelling for the same reason.
What is the difference between MAM, MTPLM and MIRO?
Maximum authorised mass is the vehicle's legal maximum loaded weight. MTPLM is the equivalent term used for caravans. Mass in running order is the vehicle as supplied, usually including a nominal driver and some fuel. Payload is the difference between them, and it is what you have to work with.
Can I uprate my motorhome?
Sometimes, by replating to a higher maximum authorised mass, where the chassis and axles permit it. Specialist companies carry this out. It may change the licence category required to drive it, the speed limits that apply and, above 3,500 kg, the tolling and ferry classifications — so the consequences extend well beyond the weight figure.
Is what I enter stored?
No. Weights are processed in your browser and never transmitted or retained.
Related tools
References
- GOV.UK — vehicle weights, overloading penalties, replating and licence categories
- Health and Safety Executive — safe loading and weight distribution
Sources are checked at publication and can change — how I choose and check references.