When you're loading up a trailer — whether it's full of building kit, motorbikes or hay bales — most people focus on how much they’re carrying. But there’s another number that matters just as much: the Unladen Weight.
This one often gets overlooked, but it plays a big role in whether you’re towing safely (and legally).
Let’s break it down.
What Is Unladen Weight (ULW)?
Unladen Weight, sometimes called kerb weight, is the weight of your trailer when it’s completely empty.
That means:
No cargo
No tools
No gear
Just the trailer itself, as it was built
It usually includes permanent fixtures (like ramps or storage compartments), but not any removable add-ons or payload.
Why Is ULW Important?
Because it’s the starting point for every legal and safety calculation when towing.
You need the ULW to figure out:
Your maximum payload (how much you can legally load into the trailer)
Whether your tow vehicle can handle it
If you're exceeding your towing limits
How Do You Calculate Payload With ULW?
Here’s the formula:
Payload = Gross Trailer Weight (GTW) – Unladen Weight (ULW)
Example:
Gross Trailer Weight = 2700 kg
ULW = 800 kg
Payload = 1900 kg
That means you can legally carry up to 1900 kg in that trailer. Go over it, and you're in overloading territory — and that’s asking for a fine (or worse).
Where Do You Find the ULW?
You might find it:
On the trailer’s data plate or sticker (usually near the drawbar)
In the manufacturer’s handbook
On the trailer’s spec sheet online
Or you can weigh the trailer empty at a public weighbridge if in doubt
What About Towing Vehicles?
Unladen Weight also applies to your car or van. Some towing laws (especially for B+E licence rules) are based on the unladen weight of the towing vehicle and/or trailer.
So if you’re right on the edge of a limit — say, with a large box trailer or plant trailer — that ULW becomes the number to check.
Brent's Tips on Unladen Weight
Don’t confuse ULW with gross weight — that includes your load.
If the trailer seems “light” when empty, it still might have a surprisingly high ULW depending on its construction.
Always check the VIN or ID plate first, and weigh it properly if you’re unsure.
Final Thought: Don’t Ignore the Empty Weight
Unladen Weight might sound boring — after all, it’s just an empty trailer, right? But knowing it can save you a load of grief when towing, especially when you’re close to capacity.
At Brent, we make it easy to see the specs, weights, and limits before you book or buy a trailer, so there are no surprises.
Need a trailer that suits your setup?
-Brent