Can your car legally tow this trailer?
Two numbers off the ad, ATM and tow-ball download, tell you the trailer's GTM, the brakes it's legally required to have at that mass, and whether it fits inside your vehicle's towing capacity and your towbar's own rating. Free tool, no account needed.
Efficient brakes required, on at least one axle
Above 750kg the trailer needs efficient service brakes. A mechanical or cable override brake on one axle is the common trade fitment in this band, though electric brakes are also fitted.
No ball weight entered, so this reads your 2000kg ATM directly. GTM (the figure the brake rule actually uses) is ATM minus the ball weight, so it will be a little lower than this once you have that number, never higher. That means this can only ever push you into a stricter tier than the truth, not a looser one.
General information from published VSB1 thresholds, not a compliance determination. Brake and mass thresholds are set nationally, but registration, inspection and towbar-fitting rules are administered state by state. The trailer's compliance plate and your vehicle's handbook are the source of truth; this tool is for sanity-checking a listing before you inspect it in person.
Reading the answer
ATM is what's advertised. GTM is what the law measures
Every trailer ad quotes ATM because it's the headline spec on the compliance plate. But VSB1, the national trailer brake standard, sets its thresholds against GTM, which is ATM minus the tow-ball download. The gap between the two is usually modest on a light trailer and can be a few hundred kilograms on a loaded tandem, so reading ATM as if it were GTM can put a trailer in the wrong brake tier on paper.
Two different limits, and both apply
Your vehicle's braked towing capacity caps the trailer's ATM. Your towbar's rated capacity, stamped on the tongue of the towbar itself, caps the tow-ball download separately. A trailer can sit comfortably under the first limit and still overload the second, particularly anything loaded nose-heavy: a loaded box trailer, a generator on a tradesman trailer, or a camper trailer packed for a trip.
What this tool can't tell you
Mass and brakes are one part of whether a trailer is safe to tow, not the whole picture. It says nothing about whether the trailer is encumbered, stolen, or has had its identity altered, and it says nothing about the physical condition of the chassis, coupling or tyres. The safety guide covers the PPSR search and the in-person checks that this calculator can't replace.
Common questions
What's the difference between ATM and GTM?
ATM (Aggregate Trailer Mass) is the trailer fully loaded, unhitched, sitting on its own wheels. GTM (Gross Trailer Mass) is ATM minus the tow-ball download, which is the weight the coupling transfers onto your tow vehicle. Ads almost always quote ATM; the brake rules are written against GTM, which is why this tool asks for both.
When does a trailer legally need brakes?
Under VSB1, a trailer at or below about 750kg GTM needs no brakes at all. From 750kg to 2000kg GTM it needs efficient brakes, commonly a mechanical override brake on one axle. Above 2000kg GTM it needs brakes on every wheel, operable from the driver's seat, plus a battery-powered breakaway system that holds the brakes on for at least 15 minutes if the trailer comes off the tow vehicle. NSW also requires a breakaway battery-charge monitor above 2000kg.
My tow vehicle's towing capacity is higher than the trailer's ATM. Am I fine?
Check the tow-ball download against your towbar's own rated capacity as well. A trailer well inside your vehicle's overall towing capacity can still put more download on the tow ball than the towbar is rated for, especially a trailer loaded nose-heavy. Both limits apply.
Does a clean answer here mean the trailer is legal and clear to buy?
No. This tool checks mass against published brake and towing thresholds, nothing else. It doesn't check the trailer's compliance plate matches its VIN, and it doesn't search the PPSR for money owing or a stolen report. Read the safety guide before you pay.
Know it fits? Go find one.
Every trailer listing here carries its ATM and brake type as a structured field, so you can filter to what your vehicle can actually tow.
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