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 simplified formula (Berto-style): Front PSI = 0.85 × Rear PSI (front carries less weight) Rear PSI ≈ Rider weight / Tire width factor
Tire width “factor” (lower = higher PSI):
| Tire Width | Factor (kg basis) | Approximate PSI per kg |
|---|---|---|
| 23 mm road | 1.7 | ~0.95 |
| 25 mm road | 1.6 | ~0.85 |
| 28 mm road | 1.5 | ~0.75 |
| 32 mm gravel | 1.3 | ~0.6 |
| 38 mm gravel | 1.1 | ~0.5 |
| 45 mm gravel/MTB | 0.95 | ~0.4 |
| 2.1 in MTB | 0.6 | ~0.25 |
| 2.4 in MTB | 0.45 | ~0.18 |
| 2.6 in MTB | 0.35 | ~0.15 |
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): Use a rear bias of 0.9× front (less front-end deflection)
- 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