Tire Pressure for Load Calculator

How it is calculated

The tool scales the tire's maximum pressure by how heavily the tire is loaded: ratio = load ÷ max load, then psi = ceil(ratio × max psi × 1.10). The 10 percent safety margin is built in and the result is always rounded up to a whole psi, but it is never allowed above the tire's own maximum pressure, so a tire loaded to 90 percent or more of its capacity simply shows the maximum. Load and max load must use the same unit (pounds or kilograms) and are per tire; max psi comes from the sidewall. The load is also shown as a percentage of capacity. All three values must be above zero, and a load above the tire's maximum gives no result. There is no lower limit, so a very light load gives a very low figure (18 percent of capacity shows 9 psi in the sample tire) that may be below what the vehicle maker requires. The scaling is a straight proportion, a simplification that does not replace the vehicle placard or the manufacturer's load-inflation tables.

Common mistakes

• Entering the total vehicle or axle weight instead of the load on one tire. The tool works per tire, so divide an axle load by the number of tires on it.
• Mixing units, such as the load in kilograms and the max load in pounds. The ratio then makes no sense; use the same unit for both.
• Reading 44 psi at 90 or 100 percent load as a calculated figure. Above roughly 91 percent of capacity the margin would exceed the tire's limit, so the tool just shows the sidewall maximum, which you must never go over.
• Entering a load slightly above the rating and expecting a number. A load higher than the max load gives no result at all, because the tire is overloaded.
• Taking the max psi from the door sticker. Use the maximum inflation pressure moulded on the tire sidewall, and set pressures cold: a tire that has just been driven reads several psi higher.