Most pressure charts give you a single number based on tire width and rider weight. Real-world pressure depends on five more things: system weight, surface, tubeless vs tube, rim width and ride style. This calculator adds all five and gives you a target plus a tight upper/lower bound so you can experiment safely.
Lower pressure means a larger contact patch, which grips better and absorbs road buzz. Higher pressure means less rolling resistance on smooth tarmac but a harsher ride and worse grip on rough surfaces. The right number is the lowest pressure where the tire still feels stable under hard cornering and sprinting.
The classic rule of thumb (load / tire width = psi) is wrong for two reasons: it ignores rim width (which sets the tire's casing shape) and ignores surface roughness. Modern wide-hookless rims at 25 mm internal width let you run 5-10 psi lower than the old 19 mm narrow rims.
Without a tube, there's no risk of pinch-flat at lower pressures (in normal conditions), so you can run 5-10 psi lower and gain grip and comfort. With a tube, you need a buffer for potholes.
No. The rim is engineered for a specific range; exceeding the max risks catastrophic failure. We warn if your answer is over a reasonable hookless max.
The calculation still works. You'll get a lower recommended pressure. Most lightweight riders run 55-70 psi front and 65-80 psi rear on 28 mm tires.
Because "perfect" depends on conditions you can feel in the moment. The range is your safe experiment space: start at the recommended pressure, then try ±2 psi and see if the tire feels better in corners or on the rough patch.
This calculator was built to answer a question most online versions skip or oversimplify. It runs entirely in your browser; no inputs are stored or transmitted. The math is grounded in standard cycling physics and physiology models, and is suitable for hobbyist and intermediate training use. It is not a substitute for a coach, sports scientist, or professional bike-fit service.
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Children under 13 are not the intended audience.
This calculator is provided for general informational and educational purposes only. It is not medical, mechanical, or legal advice. Predicted values depend on inputs you supply and simplified physical models; real-world outcomes vary. Use at your own risk. Brand names are descriptive only and do not imply affiliation.