GVM upgrade calculator: what you gain and what you lose

See how a GVM upgrade changes your payload and how much you can still tow, with and without a GCM upgrade.

Short answer A GVM upgrade adds payload, but it doesn't change your braked towing capacity, and on its own it doesn't change your GCM. So if you load the vehicle up to its new GVM, the heaviest trailer you can tow goes down by about the same amount. It only helps towing if payload, not GCM, was your limit.

Start from your vehicleOptional. Fills in the manufacturer's figures, which you can still change.

Vehicle not listed? Enter the figures from its compliance plate or owner's manual below. See all vehicles.

Your vehicle todayFrom the compliance plate, owner's manual or manufacturer specs
The upgradeFrom the upgrade kit or certifier's paperwork

What a GVM upgrade does and doesn't change

  • GVM goes up. The loaded vehicle, including the towball download, can legally weigh more.
  • GCM stays the same unless it's re-rated separately. Western Australia's Department of Transport says GCM can't be re-rated unless specific requirements are met and approved.
  • Braked towing capacity doesn't change. WA's Department of Transport says only the manufacturer can re-rate it.

That's why a GVM upgrade can make towing harder, not easier. The vehicle and trailer still have to fit under the same GCM, so weight you add to the vehicle comes off the trailer.

Worked example

A ute with a 3,200 kg GVM, 6,000 kg GCM, 3,500 kg towing capacity and 2,200 kg kerb weight gets a GVM upgrade to 3,500 kg. GCM stays at 6,000 kg.

  • Payload goes from 1,000 kg to 1,300 kg, a 300 kg gain.
  • Loaded to the old 3,200 kg GVM, it could tow about 3,111 kg. Loaded to the new 3,500 kg GVM, only about 2,778 kg, roughly 333 kg less. (With a 10% towball download, (GCM − GVM) ÷ 0.9.)
  • Towing the full 3,500 kg, the GCM leaves 6,000 − 3,500 = 2,500 kg for the ute, so only 300 kg of payload, before and after the upgrade.

The upgrade helps when the ute is heavy and the trailer is light. When the trailer is heavy, GCM is the limit and the upgrade adds nothing.

Pre-registration and post-registration upgrades

According to WA's Department of Transport, a pre-registration upgrade on a new vehicle must be fitted by a modifier with federal Second Stage Manufacturer approval. A post-registration upgrade on a vehicle already on the road needs state approval, which in WA means a modification permit. Other states run their own approval processes, and rules have changed recently, so check with your state's transport department and your certifier.

A GVM upgrade can also affect your warranty and insurance. WA's Department of Transport suggests checking with the manufacturer and your insurer first.

To check a full setup after an upgrade, use the towing calculator with your new GVM, or the payload calculator to see what you can carry.

Common questions

Does a GVM upgrade increase towing capacity?
No. Western Australia's Department of Transport says braked towing capacity can only be re-rated by the manufacturer, so a GVM or GCM upgrade doesn't change it. A GVM upgrade on its own also leaves the GCM where it was.
Can a GVM upgrade reduce what I can tow?
Yes, once you use the extra GVM. If the GCM stays the same, every extra kilogram in the vehicle comes off the trailer you can tow. WA's Department of Transport warns that upgrading GVM without upgrading GCM will reduce the trailer weight you can tow with the vehicle loaded to its new maximum.
What's the difference between a pre-registration and post-registration GVM upgrade?
A pre-registration upgrade is fitted to a new vehicle before it's first registered, by a modifier with federal Second Stage Manufacturer approval. A post-registration upgrade is fitted to a vehicle already on the road and needs state approval, for example a modification permit in WA. Each state sets its own process.
Can I upgrade GCM too?
Sometimes, but it's a separate approval. In WA, GCM can only be re-rated when specific technical bulletins are met and the Department of Transport approves it, and a GVM approval doesn't cover it. Enter the new GCM above if your upgrade includes one.
Is a GVM upgrade worth it for towing?
It's worth it if your problem is payload: too much weight in the ute or 4WD, including the towball download. It won't help if your problem is GCM, which is common when towing near the maximum. The calculator shows which one you're up against.

Sources

Rules checked against these sources on 12 October 2026. See rules, sources and method.

Check your own plates. This calculator uses the numbers you enter. Your limits come from your vehicle's compliance plate and owner's manual, your trailer's plate and your towbar's rating. The only way to know your real weights is to weigh the loaded rig at a public weighbridge.

Towing guides

Towing specs by vehicle

Published towing capacity, GVM and GCM for every variant, from each maker's own spec sheet.