What Gearing Do I Need for Hills?
Struggling up steep hills, grinding the pedals at 50 rpm? It might not be your legs. It might be your gearing. Here's how to work out what gearing you need, in plain English.
Why cadence matters on climbs
Most riders are most efficient between about 75 and 95 pedal revolutions per minute (rpm). Drop much below 70 rpm and every pedal stroke becomes a heavy push that tires your muscles faster. On a climb your speed drops, so you need an easier (lower) gear to keep your cadence up.
How fast will you actually be climbing?
A typical club rider holding about 2.5 watts per kilo goes roughly this fast on different gradients:
| Gradient | Speed | Gear ratio for 80 rpm |
|---|---|---|
| 6% | 11.8 km/h (7.3 mph) | 1.16 |
| 8% | 9.3 km/h (5.8 mph) | 0.90 |
| 10% | 7.6 km/h (4.7 mph) | 0.74 |
| 12% | 6.4 km/h (4.0 mph) | 0.63 |
The gear ratio is simply chainring teeth divided by cog teeth. So a 34-tooth chainring with a 28-tooth cog is 34 ÷ 28 = 1.21.
What common setups give you
| Easiest gear | Ratio | Speed at 80 rpm (700×28c) |
|---|---|---|
| 39 × 28 (standard) | 1.39 | 14.3 km/h |
| 34 × 28 (compact) | 1.21 | 12.4 km/h |
| 34 × 32 | 1.06 | 10.9 km/h |
| 34 × 34 | 1.00 | 10.3 km/h |
| 30 × 34 (sub-compact) | 0.88 | 9.0 km/h |
| 40 × 44 (1x gravel) | 0.91 | 9.3 km/h |
| 40 × 52 (1x wide range) | 0.77 | 7.9 km/h |
Put the two tables together and the picture is clear. A classic 39×28 is fine for rolling roads, but on sustained 8% climbs most club riders will be spinning far too slowly. A compact 34×32 or a sub-compact 30×34 keeps you near 80 rpm on real mountains.
Check your own bike in 30 seconds
- Open our gear ratio and cadence calculator.
- Tap your chainrings and cassette (or type the teeth), choose your tyre size and enter your usual cadence.
- Look at the "Easiest gear" speed, then compare it with your speed on your local climbs. The climb time estimator tells you that speed if you know your power.
If your easiest gear is faster than the speed you'll be climbing, it's time for a bigger cassette or smaller chainrings. Your knees will thank you.
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