Cycling Tire Pressure Calculator
Calculate optimal bike tire pressure by rider weight, tire width, and surface.
Get PSI ranges for road, gravel, MTB, and tubeless setups for grip and comfort.
Bike Tire Pressure Calculation
Modern tire pressure science (Silca, ENVE, Frank Berto) recommends much lower pressures than the sidewall maximum. Lower pressure = better grip, comfort, and often lower rolling resistance on real-world rough roads.
The formula
Pressure scales with the load and falls off steeply as the tyre gets wider, because a wider tyre holds up the same rider on a bigger air volume:
Rear PSI = 1.084 × total weight in kg × (25 ÷ tyre width in mm)^1.71
Front PSI = 0.85 × Rear PSI, since the front wheel carries less of you.
The exponent is what people underestimate. Going from 25 mm to 32 mm is only a 28% wider tyre, but it drops the correct pressure by a third.
What that gives for an 83 kg rider and bike (tubed, smooth road):
| Tyre | Front | Rear |
|---|---|---|
| 23 mm road | 88 | 104 |
| 25 mm road | 77 | 90 |
| 28 mm road | 63 | 74 |
| 32 mm gravel | 51 | 59 |
| 38 mm gravel | 37 | 44 |
| 45 mm gravel | 28 | 33 |
| 2.1 in MTB | 21 | 25 |
| 2.4 in MTB | 16 | 19 |
| 2.6 in MTB | 14 | 17 |
Adjustments:
- Tubeless: Drop 5-10 PSI from tubed values (less pinch flat risk)
- Rough surface / gravel: Drop 10-20% — more grip, less fatigue
- Wet conditions: Drop 5-10% for grip
- Heavy rider (over 200 lb): narrow the front-to-rear gap, front at about 0.9× rear rather than 0.85×, to stop the front deflecting under braking
- Bikepacking with full load: Add 10-15 PSI to baseline values
Sweet spots by discipline:
- Road racing 700×25c, 75 kg rider: 75-85 PSI front / 85-95 PSI rear
- Gravel 700×40c, 75 kg rider: 35-45 PSI front / 40-50 PSI rear
- XC MTB 29×2.25, 75 kg rider: 18-22 PSI front / 20-24 PSI rear
- Trail MTB 27.5×2.5, 75 kg rider: 22-26 PSI front / 24-28 PSI rear
The “drop test”: Sit on the bike with normal kit. Tire should compress about 15% of its inflated height at the contact patch — that’s the sweet spot for low resistance + impact compliance. Less compression = too high. More = too low.
Dangers of running too low:
- Pinch flats (tubed) or burping (tubeless)
- Rim damage on hard impacts
- Sidewall cuts from cornering forces
- Squirmy handling at speed
Dangers of running too high:
- Hard ride, washboard chatter
- Reduced cornering grip
- Slow rolling on rough roads (counter-intuitive but true!)
- Pinch flat risk paradox: hard tire = more force into the rim
How we build and check this calculator
This calculator runs entirely in your browser, so the numbers you enter stay on your device. The math behind it is written by hand and tested against worked examples and standard references before the page goes live.
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