How the comparison works
The reading and both stated figures are converted to kilopascals, so the comparison works whichever unit you chose. One psi is 6.894757 kilopascals and one bar is 100 kilopascals.
The verdict is below, within or above the range, and the adjustment is the distance to the nearest end, reported in the unit you entered.
Worked example
A gauge shows 30.0 psi and the tyre states 35 to 45 psi. The reading is 5.0 psi below the range, so the suggested adjustment is to add 5.0 psi. The same reading is 2.07 bar or 207 kPa.
These figures are illustrative. Use the range printed on your own tyre sidewall or the rim maker's chart.
Why pressure is not set from rider weight
A heavier rider usually runs more pressure, but the safe range depends on the tyre volume, the rim, the surface and whether the bike is tubeless. A narrow road tyre and a wide gravel tyre at the same pressure behave completely differently.
The tyre sidewall gives a maximum, and the rim maker often gives a narrower recommended range. Where they disagree, use the lower of the two maxima and check the rim's own limit.
Limits of this calculator
It compares numbers; it does not know your tyre, rim, load or terrain. It does not account for a faulty gauge, slow punctures, tubeless sealant loss or the temperature change between indoors and the road.
For a car, use the car tyre pressure calculator.
For a car tyre and a vehicle placard, use the UK tyre pressure calculator.
Inputs for the bicycle tyre pressure calculator
Pressure unit
Choose the unit on your pump gauge. The result converts the reading to the other two units.
Measured tyre pressure
The reading from your gauge, taken before the ride.
Lowest stated pressure
The lower figure on the tyre sidewall or the rim maker's chart.
Highest stated pressure
The upper figure for the same tyre, rim and load condition.
CALCULATOR QUESTIONS
Bicycle tyre pressure calculator UK questions
Should I use the pressure printed on the sidewall?
That is usually a maximum, not a recommendation. Check the rim maker's range as well and stay within both.
Why do wider tyres run lower pressure?
A larger air volume carries the same load at lower pressure, which also gives more comfort and grip.
Does temperature matter?
Yes. A tyre inflated indoors is softer in the cold, and a tyre warmed by braking or sun reads higher.
What about tubeless setups?
They often run lower pressures, but the rim's minimum matters. Follow the rim and tyre maker's figures rather than a general rule.