CalculatorsTire Pressure Calculator
Tire Pressure Calculator
Wider tyres and lighter riders want less pressure. This splits system weight 45% front and 55% rear, then scales for gravel and MTB. It is a starting pump figure, not a Silca pressure table.
Inputs
Results
Please tick the box above to display the Result.
How the number is made
PSI per axle ≈ (axle weight in pounds ÷ tyre width mm) × 21 × surface factor. Road factor 1, gravel 0.72, MTB 0.65. Results are shown in bar. Hookless rims are capped at 5.0 bar (72.5 psi). Example: 75 kg rider + 8 kg bike on 28 mm road tyres → 4.26 bar front, 5.20 bar rear.
Inner rim width is not an input. A wider rim usually wants less pressure, and this estimate does not apply that correction. The 45/55 weight split and the ×21 factor are a workshop start, not the Silca model. Gravel uses 0.72 × the road figure and MTB 0.65 ×; an 80 kg rider on a 14 kg trail bike with 2.4 in tyres gets about 21 psi front and 26 psi rear, near common tubeless trail starting points. Hookless results are capped at 5.0 bar (72.5 psi). Casing, inserts and luggage move the real number.
- Hookless cap applied. Yes means the raw figure was above 72.5 psi and got cut.
Width before pressure
If the tyre is not approved for the rim, the pressure is irrelevant. Run the ETRTO check with the inner rim width printed on the sidewall or rim bed.
Related calculators
- Rim and Tire ETRTO Checker
Pressure only matters after the tyre is allowed on that rim.
- Tubeless Sealant Calculator
A tubeless setup needs fluid in the tyre you just pressurised.
Questions
Why is the rear higher?
More of your weight sits on the rear wheel. The split here is 55% rear, 45% front.
What is the hookless limit?
The ETRTO and ISO limit for hookless road rims is 5 bar / 72.5 psi, and some rims are rated lower. This calculator will not print a higher starting pressure for them.
Does rim inner width change the PSI?
On the bike, yes: a wider rim spreads the tyre, and a wider tyre needs a little less pressure. This calculator does not model the rim; it uses axle weight, labelled tyre width and a surface factor. If the tyre measures wider than its label on your rim, enter the measured width.
Example products
Product links are Affiliate Links to Amazon websites. Using them does not cost you anything extra, and if you make a purchase we may receive a commission. Details: Terms of Service, point 5.
- Track pump with a gauge
A frame pump gauge is too coarse for a 0.2 bar change.
$30–$80
- Digital pressure gauge
Check the pump gauge. They drift.
$20–$40