MTPLM, MiRO, MAM and Payload Explained: UK Caravan Weights

Caravan weight plates carry a small alphabet of acronyms, and the one that catches people out is not the term they cannot read — it is MAM, which means two different things depending on whether you are reading the caravan's plate or the car's. This guide separates MTPLM, MiRO and payload from the car-side MAM, runs one illustrative outfit through every limit, and shows which check actually bites first.

What does MTPLM mean?

MTPLM stands for Maximum Technically Permissible Laden Mass — the absolute maximum weight your caravan is allowed to be when fully loaded for the road. The manufacturer sets it and stamps it on the caravan's weight plate, normally near the entrance door or inside the gas locker. It already includes the user payload, all fluids such as fresh water, and the personal belongings you carry — clothes, food and the rest. Go over it and the caravan is over its legal weight.

You will also see MTPLM called the caravan's MAM (maximum authorised mass). Before 1998 the same figure was the maximum gross weight (MGW), so older handbooks and adverts may still use that term. They all point at the same number: the ceiling the loaded caravan must not cross.

What is MiRO (MRO), and what does it include?

MiRO — mass in running order, now usually written MRO — is the weight of your caravan as it left the factory to the manufacturer's standard specification. It appears on the weight plate alongside the MTPLM. The term shifted from MiRO/MIRO to MRO over recent years; one manufacturer's own page heads the entry "MRO (formerly MIRO)". Both mean the same factory running-order weight, and people type it every way: MIRO, MiRO, MRO and "mass in running order".

MiRO is not the bare shell. For an NCC-Approved caravan built from 2011 it carries an allowance for basic equipment such as a gas bottle and the electrical hook-up cable. Older caravans include different items, so the handbook is the only reliable list.

Water is where owners get caught out. Since 2015 manufacturers state how much fresh water sits in the MiRO figure, and most have chosen to include zero — covering storage tanks, water heaters and the pipework. So do not assume your MiRO already accounts for a full tank. Often it accounts for none, and a brimmed tank is roughly 1 kg per litre out of your payload. Check the handbook for your model.

The difference between those two stamped numbers is the only weight you control: your payload.

How do I calculate my caravan's user payload?

Your payload is MTPLM minus MiRO — the manufacturer never prints it on the plate, so you work it out yourself. It is the allowance for everything you add to a van that left the factory at its MiRO weight.

On the illustrative outfit this guide uses throughout, the caravan has a MiRO of 1,250 kg and an MTPLM of 1,500 kg, so the payload is 250 kg (1,500 − 1,250). That 250 kg has to cover the awning, the bedding and crockery, the food, the leisure battery if your retailer fitted it rather than the factory, any motor mover, and the water you carry. It is gone faster than most first-time owners expect.

A few things eat payload silently. A leisure battery counts towards MiRO only when the caravan manufacturer supplied it; a retailer-fitted battery comes straight out of your payload instead. Dealer-fitted extras — a motor mover, solar, air conditioning — push the real weight above the published MiRO without changing the plate. Many buyers fixate on the MTPLM, never check the MiRO, and then find they have surprisingly little room for gear. The figures on a poster, in a brochure and on the plate can all differ, so the plate and handbook win.

Is MTPLM the same as MAM?

Yes — and that is exactly where the confusion starts. MAM means maximum authorised mass, and the caravan's MTPLM is its MAM. The trouble is that the tow car's maximum gross weight is also called its MAM (you will also see it as GVW or maximum permissible weight). One acronym, two referents.

So when a towing source says "MAM", read which side it is talking about. On the caravan it is the MTPLM. On the car it is the loaded-car ceiling that, together with the caravan, must fit under the gross train weight.

What is gross train weight, and how does the combination rule work?

Gross train weight (GTW) is the weight of the fully loaded car plus the fully loaded caravan, and it must not be exceeded — it is usually the limit that bites first. GOV.UK puts the rule plainly, and the car's GTW is listed on its VIN plate. The legal test is on the actual weights on the day: your loaded car plus your loaded caravan against the car's GTW. As a stricter pre-trip ceiling, add the car's MAM to the caravan's MTPLM and check that total stays under GTW — if the maxed-out figures fit, the real ones will.

Here is the illustrative outfit run end to end (all figures kg; this is a composite, not a real registered rig):

Four checks have to hold at once, and on this outfit they all close:

1. Caravan MTPLM against the car's braked towing limit: 1,500 ≤ 2,000 — fine, with 500 kg in hand.
2. Car MAM plus caravan MTPLM against the car's GTW: 2,450 + 1,500 = 3,950 ≤ 4,200 — fine, but only 250 kg in hand. This is the tightest legal check.
3. Caravan MTPLM against 85% of the car's kerbweight: 0.85 × 1,900 = 1,615 kg, so 1,500 kg is a ratio of 78.9% — comfortably novice-safe, with 115 kg of margin. The 85% figure is industry guidance, not law (more below).
4. Caravan noseweight against the car/towbar maximum: 90 ≤ 100 — fine, with 10 kg in hand. The 90 kg is 6% of the 1,500 kg MTPLM, inside the recommended 5–7% band.

The lesson sits in checks 2 and 3. The headline braked towing limit of 2,000 kg has 500 kg to spare, yet the combination ceiling leaves only 250 kg and the match guideline only 115 kg. The limit that binds your outfit is rarely the big number on the brochure — a point worth its own guide, on what a car's towing limit does and doesn't prove.

How loadmate helps you stay under your MTPLM

You now know what each term means and how the four checks fit together. The live question is the one a definition cannot answer: does the caravan you are looking at actually sit under your own car's limits, and which of the four runs out first? Can I Tow It? in the loadmate app settles that. You enter the caravan's MTPLM and MiRO and the car's MAM, braked towing limit and noseweight limit, and it runs the same checks this guide just walked through, then tells you whether the outfit is within its limits or over — and names the limit that is tight. It works from the figures you type, flagged as a spec-based estimate. It is free in the app with no account needed, so you can test a real pairing rather than theory. Saving and tracking your own outfit over time is the loadmate Pro step.

loadmate provides decision support for towing safety, not legal weight certification. For legal weight evidence, use a certified weighbridge. Towing remains the operator's responsibility — see /safety-disclaimer. If you want to check a specific pairing now, the free Can I Tow It? check lives at /tow-check.

Where do I find my caravan's MTPLM and MiRO?

Both are stamped on the caravan's weight plate — normally close to the entrance door, though some makers now fit it inside the gas locker — and repeated in the handbook. Payload is the one figure you will not find printed anywhere; you derive it by subtracting MiRO from MTPLM.

On the car side, the MAM is on a plate or sticker and in the handbook, and the gross train weight is on the VIN plate. For Great Britain the handbook, specification sheet and the vehicle's plate are the reliable sources for towing weights.

Noseweight versus payload — what each one limits

Noseweight and payload are different numbers doing different jobs, and people muddle them. Payload is how much weight you may add inside the caravan. Noseweight is the downward force the caravan's hitch puts on the car's towball once it is loaded — a question of where the weight sits, not how much there is.

Noseweight should sit in the region of 5–7% of the caravan's actual laden weight, which on the 1,500 kg illustrative van is about 75–105 kg; the worked 90 kg lands in the middle. That band is guidance for stability, not a legal figure. The hard cap is the lowest of four physical limits — the car's towbar and ball, the car's own noseweight limit, the caravan's drawbar limit and the caravan's hitch coupling — so the lowest of those four is the one you must not exceed. Setting noseweight correctly is its own topic; the full method, with how to measure it and which of the four limits caps it, is in our guide to caravan noseweight. Treat this as the short version.

Is the 85% rule a law, and what about my licence?

No — the 85% rule is the caravan industry's recommendation for less experienced tow-car drivers, not a legal limit. It says a novice should keep the caravan's MTPLM to no more than 85% of the tow car's kerbweight, rising towards 100% with experience. It is a sensible stability guideline, and it is subordinate to the legal limits: the NCC is explicit that the combined MAM "takes preference" over the weight ratio. On the illustrative outfit the ratio is 78.9%, so it sits inside the novice guideline as well as under every legal ceiling. Whether a particular car and caravan go together is a decision in its own right — our guide to matching a tow car to a caravan and the 85% rule runs the full five checks.

On licences, the GB rules changed in 2021. DVSA stopped running the separate car-and-trailer (B+E) test on 20 September 2021, and the law came into force on 16 December 2021. Since then a category-B licence passed from 1 January 1997 lets you tow a trailer up to 3,500 kg MAM without that extra test. Drivers who passed before 1 January 1997 can usually drive a car-and-trailer combination up to 8,250 kg MAM. Your licence category is one more ceiling the outfit has to fit under.

What happens if my caravan is over its MTPLM?

An overloaded outfit can be stopped at the roadside: DVSA can issue an immediate prohibition notice and may immobilise the vehicle. A car with a trailer is treated as two separate units, so the car and the caravan can each be prohibited at the same time, and a prohibition can keep you off the road until the problem is fixed.

There are graduated fixed penalties for overloading: less than 10% over is £100, 10% to under 15% is £200, and 15% or more is £300. Examiners allow a 5% leeway before acting, but that is examiner discretion, not a legal allowance, and it does not apply once the excess reaches 1 tonne. Serious overloading — 30% or more over, or 5 tonnes of excess — draws a court summons instead of a fixed penalty. The driver is responsible for the outfit being within its limits. Overloading may also affect an insurance claim, so it is worth keeping clear of the limits rather than skirting them.

Related guides

This pillar defines the terms; each spoke takes one of them deeper:

• Caravan noseweight: how to measure, set and stay legal — the deep dive on the download at the towball: hitting the 5–7% band, the lowest-of-four cap, and how packing changes it.
• Can my car tow a caravan? Tow-car matching and the 85% rule — the five checks that decide a pairing, and where the 85% kerbweight ratio sits beneath them.
• How to weigh a caravan at a public weighbridge — turning these plate limits into measured weights, and why a hitched van reads lighter than it really is.
• How to load a caravan: axle weights and noseweight — where the payload goes once you have it, and the axle rating that sits alongside the MTPLM.
• Maximum towing weight: what it does and doesn't prove — why a generous towing rating says nothing about whether your loaded outfit clears the combination rule.