Towing weight calculator
Towing has several separate limits, and it is easy to be inside three of them while over the fourth.
% of trailer
Within all limits
1
- Tongue or nose weight
- 250.0
- Loaded vehicle weight
- 2750.0
- Payload remaining
- 150.0
- Gross combination weight
- 5000.0
- Headroom under the combination limit
- 1000.0
- Largest trailer these limits allow
- 3500
Show the working
- Vehicle kerb weight = 2200
- Gross vehicle mass limit = 2900
- Gross combination mass limit = 6000
- Loaded trailer weight = 2500
- Tongue weight = 10
- Occupants and cargo = 300
- Tongue or nose weight = 2500 * 10/100 = 250
- Loaded vehicle weight = 2200 + 300 + 250 = 2750
- payload_capacity = 2900 - 2200 = 700
- payload_used = 300 + 250 = 550
- Payload remaining = 700 - 550 = 150
- Gross combination weight = 2750 + 2500 - 250 = 5000
- Headroom under the combination limit = 6000 - 5000 = 1000
- Largest trailer these limits allow = min(6000 - 2750 + 250, (700 - 300) / (10/100 > 0 ? 10/100 : 1)) = 3500
- Within all limits = 2750 <= 2900 && 5000 <= 6000 ? 1 : 0 = 1
Values are shown to six significant figures here; the arithmetic itself runs on exact fractions and is only rounded where a number is printed.
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The formula
- tongue weight counts against the vehicle payload, not the trailer
- gross combination = loaded vehicle + trailer - tongue weight, since the tongue is already on the vehicle
Tongue weight below about 8% of the trailer weight invites sway, which is the failure mode that causes most towing accidents.
These are the manufacturer plate limits. Local licensing rules may cap you lower still.