What Height, Weight and Length to Put in a Motorhome Sat Nav
Enter the measured height of the tallest thing on your roof, rounded up to the next 10 cm; the plated maximum weight, not what the van weighs today; the overall length including the bike rack; and the body width. Those four numbers – five with axle load – are what the sat nav routes on. Get them right once and you can mostly forget about them. Get one wrong and the unit is confidently guiding the wrong vehicle.
I talk customers through these numbers every week, and the same handful of mistakes come up again and again. So here's how I'd do it, with a tape measure and the plate, before the first trip.
The five numbers at a glance
| Number | What to enter | Where it comes from |
|---|---|---|
| Height | Tallest fixed point on the roof, rounded up to the next 10 cm | Tape measure, van level and unladen – never the brochure |
| Weight | Plated maximum (3,500 kg, 3,850 kg, 4,250 kg…), not today's weight | The plate in the door frame or engine bay, or the V5C |
| Length | Bumper to the last thing bolted on – bike rack with bikes, towbar, ladder | Measure it loaded for a trip |
| Width | Body width, mirrors excluded | Spec sheet or V5C |
| Axle load | Maximum for the heaviest axle | Same plate |
Height: measure it, don't read it
The brochure height is the bare shell. The moment you add a satellite dome, an air-conditioning unit, a roof box, solar panels on brackets or a TV aerial that stays up, you're taller than the brochure – sometimes by 20 cm or more. Measure the highest point with the van level and unladen, then round up to the next 10 cm. If the tape says 3.14 m, enter 3.20 m.
Why round up rather than down? Because a bridge signed at 3.2 m has a bit of margin built in and your tyres and suspension change by a centimetre or two anyway. A 10 cm margin costs you nothing on a route. A 2 cm shortfall costs you the roof.
Good to know: if your motorhome's travelling height is over 3 metres – and most coachbuilts and A-classes are – the law requires the height to be displayed in the cab. A label on the dash is also the quickest way to remember the figure you entered.
Straight off a CMNAV screen. The vehicle profile lives in the settings menu and it's the first thing to fill in – before the first postcode.
Weight: the plated figure, every time
This is the one people get wrong most. Enter the maximum authorised mass on your plate – 3,500 kg for a standard 3.5-tonner, 3,850 or 4,250 kg if yours has been uprated, more for a tag-axle – not whatever you think the van weighs with the water tank half full.
UK weight-limit signs refer to the maximum gross weight a vehicle is allowed to be, not what it weighs at that moment. A "3T" weak-bridge sign applies to an empty 3.5-tonne motorhome just as much as a full one. So the sat nav needs the plated number to keep you legal, and it never needs changing between trips.
If you've had the van uprated, enter the new plated figure. If you tow a trailer or an A-frame car, that's a separate profile – the units switch between profiles, and routing always follows whichever one is active. There's more on how that works under Features in the FAQ.
Length: include the thing on the back
Overall length is bumper to the last thing bolted on – the bike rack with the bikes, the towbar, the rear ladder if it sticks out. A 7.0 m van with a loaded rack is a 7.4 m van. Length matters less often than height and weight, but on a tight rural junction or a length-restricted road it's the difference between going round and reversing out.
Width: body width, and a dose of realism
Enter the body width from your spec – typically 2.2 to 2.35 m for a coachbuilt – not the mirror-to-mirror figure. Legally, mirrors aren't counted in a vehicle's overall width, and width-limit signs are set against body width. In practice, a 6'6" (2.0 m) restriction has posts, and your mirrors will find them. So I set the profile to body width and treat any width-restricted lane as somewhere I'd rather not be in a motorhome, whatever the maths says.
Axle load
Take the heaviest axle figure from the same plate. It's rarely the thing that triggers a diversion in the UK, but it's on the plate and it takes ten seconds, so fill it in.
The mistakes I see every week
- Brochure height. The single most common one. The dome or the air con was never counted.
- Feet and inches versus metres. Someone enters 10 (feet) into a field expecting metres, or 3.2 into a field expecting feet. Check the units screen first.
- Kilograms versus tonnes. "3.5" in a kilogram field is a very light motorhome. It should read 3500.
- Actual weight instead of plated. Covered above – it makes the unit think you're allowed over bridges you aren't.
- The wrong profile is active. If you've also got a car profile set up and used it last weekend, the motorhome is being routed as a car until you switch back. Routing is always based on whichever profile is selected.
- Short routing. Shortest distance is not the same as suitable. I recommend Easy or Fast; see the FAQ for the difference.
Important: once the profile is right, the sat nav will keep you off most restricted roads on longer journeys. On short local trips in rural or residential areas it can still suggest an unsuitable road when the map has nothing better to offer. Road signs and your own judgement come first, always.
Do you even need all this?
If your campervan is under 2 metres – a VW California, a pop-top that's down – you fit under almost every car-park barrier and every bridge, and a normal car sat nav will do. Between 2.0 and 2.6 m you're in height-barrier territory but most bridges are fine. Above about 2.6 m – panel-van conversions, every coachbuilt, every A-class – low bridges and weight limits become your problem, and a vehicle profile stops being a nice-to-have.
Which CMNAV unit takes these numbers?
All of them. Every camper model runs the same navigation software with the same vehicle profile and the same maps – UK plus 50 other European countries, with campsites and French aires already in the points of interest. The choice is about the cab and the extras, not about safety.
Most chosen
Starter Camper 7-inch
- Full vehicle profile, UK + 50 European countries
- Campsites and French aires in the POIs
- Speed cameras, postcode and coordinate search
- Works fully offline
- Free lifetime map updates
Suits: most motorhomes, most trips. The simple one.
See the Starter Camper
Starter Camper Plus 9-inch
- Same software and maps as the 7-inch
- Bigger screen for an A-class or a deep dash
- Free lifetime map updates
Suits: big cabs, or anyone who'd rather not squint.
See the 9-inch Starter
PRO Camper 7 or 9-inch
- Bluetooth phone calls through the unit
- Everything the Starter does
- Supports a wired reversing camera
Suits: anyone who takes calls on the road and doesn't want a second gadget.
See the PRO Camper
360 Camper 7 or 9-inch
- Built-in Full HD dash cam, 170° view
- Doubles as a reversing-camera monitor
- Android, Wi-Fi; Traffic version available
Suits: motorhomes and campervans where the camera stays put.
See the 360 CamperIf you want live traffic in the UK, the Traffic models take it over a hotspot from your phone; I'm upfront that it's patchier abroad, which is why a lot of customers run Google Maps alongside on the continent. The navigation itself never needs the internet – the maps are on the device.
Pro tip: write the five figures on a label inside the habitation door. The day you change vans, or lend the unit to a friend, you'll want them – and so will the next person who has to enter them.
Five numbers, ninety seconds, then forget about it
Every unit is switched on and tested by me before dispatch with the latest available maps. Measure the height, read the plate, and put the figures into the profile screen before the first trip – the tutorial video is linked in your order confirmation, and I'm on email if a figure doesn't look right.
Browse motorhome & campervan sat navsUnsure about a figure? WhatsApp me or email contact@cmnav.co.uk
Frequently asked questions
Do I enter my motorhome's actual weight or the maximum weight?
The maximum – the plated maximum authorised mass. UK weight restrictions are based on what a vehicle is allowed to weigh, not what it weighs on the day, so the sat nav needs the plated figure to keep you legal.
How do I measure my motorhome's height for the sat nav?
With the van level and unladen, measure to the top of the tallest fixed item on the roof – satellite dome, air con, roof box, raised aerial. Round up to the next 10 cm and enter that. Don't use the brochure figure; it's the bare shell.
Should I add a safety margin to the height?
Rounding up to the next 10 cm is the margin I use. More than that and you'll start losing perfectly usable roads; less and you're relying on the bridge sign being generous.
Do I include my bike rack in the length?
Yes – with the bikes on. Overall length is bumper to the last thing attached. If the rack comes off for the winter, you can leave the figure alone; a slightly long profile does no harm.
Do I need a motorhome sat nav if my campervan is under 2 metres?
Not really. Under 2 m you clear almost every barrier and bridge in the country and a car sat nav is fine. The vehicle profile starts earning its keep above roughly 2.6 m, which covers every coachbuilt and most panel-van conversions.
What if I also use the sat nav in my car?
Set up a second profile. The units route on whichever profile is active, so you switch before each journey. Tell me when you order and I'll enable both before it ships; you enter the figures for each.
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