Gravel Tire Pressure Calculator
Get exact front and rear PSI for your gravel bike, built on SILCA's tire pressure methodology and narrowed to gravel-only inputs — rider weight, measured tire width and gravel surface category from hardpack to deep, chunky gravel. Works for any tire brand, including Pirelli Cinturato Gravel and Schwalbe G-One setups. Also see the gravel bike PSI guide for full width and terrain tables.
Real-World Example
65 kg Rider · 42mm Gravel Tire — Calculator Output
Inputs: 65 kg total system weight (rider + bike + gear) · 42mm measured tire width · high-performance tubeless · moderate group ride pace
| Wheel · Surface | Front PSI | Rear PSI |
|---|---|---|
| 700C (29") · Cat 1 Gravel — hardpack / light gravel | 36.5 | 38.0 |
| 700C (29") · Cat 2 Gravel — moderate mixed gravel | 33.0 | 34.5 |
| 650B (27.5") · Cat 1 Gravel — hardpack / light gravel | 38.5 | 40.5 |
| 650B (27.5") · Cat 2 Gravel — moderate mixed gravel | 35.0 | 36.5 |
Cat 1 = hardpack dirt / light gravel. Cat 2 = moderate mixed gravel. Enter your exact inputs below for a personalised result.
Typical Scenarios
Gravel Tire Pressure: Common Examples
Hardpack vs moderate mixed gravel
A 175 lb (79 kg) total system weight running high-performance tubeless 40mm tires on hardpack dirt should run 42.5 PSI rear / 40.5 PSI front. Moving to moderate mixed gravel, the algorithm drops to 38.5 PSI rear / 37.0 PSI front — a 4 PSI reduction that lets the tire absorb texture instead of bouncing over it.
Loose, rocky gravel and tire width
The same 175 lb rider on loose, rocky gravel (Cat 3) with a 40mm tire should run 34.5 PSI rear / 32.5 PSI front. Sizing up to a 45mm tire on the identical terrain drops that further to 28 PSI rear / 27 PSI front — a 6.5 PSI reduction purely from the extra air volume, with no loss of rim protection.
Tubeless vs tubed casing on hardpack
A 175 lb rider on 40mm hardpack (Cat 1) tires running high-performance tubeless gets 42.5 PSI rear / 40.5 PSI front. Switching the same setup to a mid-range butyl inner tube reduces output to 40 PSI rear / 38 PSI front — the stiffer casing needs slightly less pressure to reach the same tire drop.
Quick Reference
Gravel PSI by Surface Category
175 lb (79.4 kg) total system weight · 40mm measured width · 700C · gravel weight distribution · high-performance tubeless · moderate group ride pace
| Surface Condition | Gravel Category | Front PSI | Rear PSI |
|---|---|---|---|
| Hardpack Dirt / Light Gravel | Cat 1 | 40.5 PSI | 42.5 PSI |
| Moderate Mixed Gravel | Cat 2 | 37.0 PSI | 38.5 PSI |
| Loose / Rocky Gravel | Cat 3 | 32.5 PSI | 34.5 PSI |
| Deep / Chunky Gravel | Cat 4 | 30.0 PSI | 31.5 PSI |
Use the calculator above for your exact weight and measured tire width. When in doubt between two surface categories, choose the rougher one.
Step-by-Step
How to Use This Calculator
- 1
Calculate total system weight
Weigh yourself fully kitted — helmet, shoes, hydration pack — and add the exact weight of your bike, including frame bags if you run them. A 155 lb rider on a 22 lb loaded gravel bike = 177 lb system weight.
- 2
Determine measured tire width
Don't use the number printed on the tire sidewall. A tire labelled 700x40c on a modern wide gravel rim (24–25mm internal) often measures 42–43mm inflated. Use calipers. Gravel tires run 28–55mm on this calculator, matching the real range sold for gravel bikes.
- 3
Select your gravel surface category
Cat 1 (hardpack dirt / light gravel) runs the highest PSI; Cat 4 (deep, chunky, loose gravel) the lowest. A single ride often crosses several categories — pick the roughest section you'll spend meaningful time on, since running too high a pressure there costs far more (bounce, control loss) than running too low costs on the smoother sections.
- 4
Select tire casing type
High-performance tubeless or latex-tube casings deform most easily and need the highest pressure in this calculator's scale to avoid casing collapse in corners. Puncture-resistant tubeless casings are stiffer and run 3–4 PSI lower for the same feel — useful on rocky, sharp gravel.
- 5
Select wheel diameter
700c is the standard gravel wheel size; 650b (27.5") is common on shorter riders and plus-tire gravel setups where a wider tire is run at the same overall wheel diameter. Smaller-diameter 650b wheels need slightly higher pressure than 700c for the same tire width and weight.
- 6
Read your front/rear split
Gravel bikes carry proportionally more weight over the rear axle than road bikes, so this calculator applies a fixed 47/53 front/rear split automatically — no separate input needed. Inflate front and rear to their own numbers; never run both tires at the rear PSI.
Methodology
Built on SILCA's Tire Pressure Methodology
This calculator uses the same impedance-breakpoint math as our full SILCA tire pressure calculator — the pro-tour methodology developed by SILCA that finds the exact pressure where added air stops reducing rolling resistance and starts costing you speed to vibration losses. Nothing about the formula was changed for gravel; only the allowed inputs were narrowed to the four gravel surface categories, 28–55mm tire widths, and 700c/650b wheels — the SILCA math itself is untouched. See the SILCA tire pressure guide for the full breakpoint theory.
Core formula
Optimal PSI = (System Weight × Width/Volume Constant)
− SILCA Gravel Surface Impedance Penalty
− Casing Stiffness Modifier
Front PSI = Rear PSI × 47/53 Gravel Weight Distribution Ratio
Variable definitions
- SILCA Gravel Surface Impedance Penalty: As the surface gets rougher, the algorithm lowers PSI to let the tire absorb bumps rather than transferring vibration into the rider. Deep/chunky gravel (Cat 4) output runs roughly 26% lower than hardpack (Cat 1) at the same system weight and tire width.
- Width/Volume Constant: Air volume increases with the square of tire width, so a 45mm gravel tire requires drastically less pressure than a 35mm tire to achieve the same casing tension. This is why using measured width — not stated width — is critical, and why this calculator's width range extends to 55mm. Because this figure already reflects your actual inflated width, there's no separate rim internal-width input needed — the two static-chart calculators that ask for rim width separately are solving for the same thing your measured width already captures.
- Casing Stiffness Modifier: Supple high-performance tubeless or latex-tube casings use coefficient 1.0 as the baseline. Mid-range tubeless reduces output by ~3%, mid-range butyl tube by ~6%, and puncture-resistant casings by ~9% — a practical range of 2–4 PSI between the most and least supple options at typical gravel pressures.
- 47/53 Gravel Weight Distribution Ratio: Gravel bikes carry slightly more weight over the rear axle than road bikes (47/53 vs 48/52), reflecting the more upright, rearward-shifted riding position typical of gravel geometry. This ratio is fixed for every result on this page — there's no separate input to set.
Worked example
155 lb (70.3 kg) system weight · 700C · moderate mixed gravel (Cat 2) · high-performance tubeless · moderate group ride pace
35mm measured tire = 47.0 PSI rear / 45.0 PSI front
45mm measured tire = 31.0 PSI rear / 29.5 PSI front (−16 PSI from width alone)
Gravel distribution (47/53 split) → front is 95.7% of rear in both rows above
What this calculator doesn't account for
Rubber compound and tread pattern aren't inputs here — an aggressive-knob tire and a file-tread tire at the same width and weight get the same output, even though knob height changes the ideal pressure slightly in practice. Ambient temperature also isn't factored in: cold air drops tire pressure over time independent of any input on this page — see the cold weather tire pressure guide for adjustment amounts. Treat this calculator's output as your starting point, then fine-tune from there.
FAQ