Towing Calculators
Boat and trailer weight.
Add the boat's dry weight, engine, fuel, water and gear to the empty trailer weight to estimate what you actually tow, then check it against the trailer's capacity and your vehicle's tow rating. Runs in your browser; nothing is sent or stored.
Inputs
Result
Fill the form and press Calculate.
Towed weight = boat dry weight + engine + fuel + water + gear + empty trailer. Fuel is the number people forget: gasoline is about 0.74 kg per litre (6.2 lb per US gallon), so a 50 gallon tank adds roughly 309 lb. Fresh water is 1 kg per litre (8.34 lb per US gallon).
Worked example
Dry boat 2,000 lb + engine 400 + 50 US gal of gasoline (about 309 lb) + 10 US gal of water (83 lb) + gear 150 = 2,942 lb on the trailer. Adding a 900 lb trailer gives 3,842 lb to tow. Against a 4,000 lb GVWR (capacity 3,100 lb) the trailer has about 158 lb to spare, and a 5,000 lb tow rating leaves about 1,158 lb.
How it works
Fuel weight = volume x density. Gasoline has a specific gravity of 0.71 to 0.77 depending on blend (this tool uses the 0.74 midpoint and shows the range), diesel is about 0.838 kg per litre, and fresh water is 1 kg per litre (0.9998 g/mL at 4 C). One US gallon is 3.785 litres.
Trailer capacity = trailer GVWR - empty trailer weight. The loaded boat, with its engine, fuel, water and gear, must fit in that number, and the total of boat and trailer must also be within your vehicle's tow rating and, with the tongue weight, its payload. Manufacturers' dry weights often leave out the engine, fuel, batteries and gear, so a scale is better than a brochure.
Sources opened 2026-10-16: Gasoline - Wikipedia (specific gravity 0.71 to 0.77); Diesel fuel - Wikipedia (about 838 g per litre); Water density - USGS (water density); Alberta Transportation, Recreational Vehicle Towing Guide (trailer GVWR minus net weight gives carrying capacity). Planning aid only, not professional, engineering or safety advice. Your vehicle, trailer, hitch and boat manuals and the weight labels on your equipment come first; when in doubt, weigh it at a public scale or ask a qualified professional.
FAQ
How much does a gallon of gasoline weigh?
Gasoline specific gravity ranges from 0.71 to 0.77, so a US gallon weighs roughly 5.9 to 6.4 lb depending on blend and temperature. This tool uses 0.74.
How do I work out my boat and trailer towing weight?
Add the boat's dry weight, engine if separate, fuel, water, gear and the empty trailer. Weigh the whole rig at a scale for a real figure.
Is the manufacturer's boat weight the weight I tow?
Usually not. Dry weights often exclude the engine, fuel, batteries and gear, and the trailer is extra.
How do I know if the trailer is big enough?
Trailer capacity is its GVWR minus its empty weight. The loaded boat must be at or below that figure.
What about tongue weight?
The tongue carries part of the total and counts against the tow vehicle's payload. Measure it, or use the tongue weight and truck payload calculators.