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Bike Tire Pressure Calculator

Get the right psi for each wheel instead of guessing at the pump.

How it is calculated

Total load is rider plus bike in kg. The front wheel carries front % × total (40 % by default, allowed 20-70 %) and the rear wheel the rest. Each wheel's load is converted to pounds and put into psi = 228.7 × width−1.75 × load(lb), where width is the tire width in mm (18-80 mm). That curve is fitted to a 15 % tire-drop relationship. The result is multiplied by 0.90 for gravel or 0.82 for rough ground, and by 0.90 for tubeless. Each wheel is clamped between 15 and 130 psi, and bar is psi × 0.0689476. An unknown surface name is treated as road.

Worked example

A 75 kg rider on a 9 kg bike, 28 mm tires, road surface, inner tubes (not tubeless), 40 % of the weight on the front. Total load is 84.0 kg, so the front wheel carries 33.6 kg and the rear 50.4 kg. For 28 mm the width factor is about 0.673 psi per pound. The front load is 74 lb, giving 50 psi (3.4 bar), and the rear is 111 lb, giving 75 psi (5.1 bar).

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Common mistakes

  • Leaving out the bike: the bike has its own field, and bottles, shoes and a bag belong in the rider figure, so the total should be the full loaded weight.
  • Typing tire width in inches or in the ETRTO number: the field is millimetres, 28 for a 28 mm tire.
  • Applying both the surface and the tubeless reduction twice by hand. They are already built in, so the gravel tubeless result is about 20 % lower than road with tubes.
  • Forgetting that low-pressure results stop at 15 psi: very wide tires on a light rider simply show 15 psi, the floor, not a calculated value.
  • Pumping the rear to the same value as the front. The two differ because the rear carries more weight, and 40 % on the front is only a default for a typical road position.

About this calculator

Correct bike tire pressure is a balance between rolling resistance, grip and pinch-flat protection, and the right number depends on rider weight, tire width and the surface being ridden — wider tires and rougher or off-road surfaces call for lower pressure, while narrower tires and smooth pavement can run higher. Modern guidance, popularized by tire and component makers, generally targets a tire 'drop' — how much the tire compresses under the rider's weight — of around 15%, and tubeless setups can safely run noticeably lower pressure than tubed tires since there's no risk of pinch-flatting a tube against the rim.

Cyclists, bike fitters and shop mechanics use pressure guidance like this to move riders away from guessing or defaulting to the max-PSI number printed on the sidewall, which is almost always too high for comfort and grip on real road or trail surfaces. Front and rear pressures are also typically set a few PSI apart, since the rear wheel carries more of the rider's weight.

Your weight, tire width, the surface you ride on and whether you run tubeless are turned into suggested front and rear pressures in psi and bar.

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