What gearing for climbs? Chart by gradient and power

Whether your easiest gear is low enough for a climb can be calculated. Here you find the gear ratio you need for a given power and gradient, what common combinations offer and what to check when changing parts.

For your weight, power and drivetrain: open the gear calculator →

Gear ratio needed by gradient and power

Largest ratio of front teeth to rear teeth that still lets you pedal at least 80 rpm. Calculated for 84 kg total, road bike, 700C with 28 mm tires and steady power. Speed in km/h in brackets.

Power	6 %	8 %	10 %	12 %	15 %
150 W	0.94 (9.6)	0.73 (7.5)	0.60 (6.1)	0.50 (5.1)	0.41 (4.2)
200 W	1.23 (12.6)	0.96 (9.9)	0.79 (8.1)	0.67 (6.8)	0.54 (5.5)
250 W	1.50 (15.3)	1.19 (12.2)	0.98 (10.0)	0.83 (8.5)	0.68 (6.9)
300 W	1.75 (17.9)	1.41 (14.4)	1.17 (11.9)	0.99 (10.1)	0.81 (8.3)

What common easiest gears offer

Smallest chainring at the front, largest cog at the rear. The smaller the value, the easier. If it is at or below the value in the chart above, you get up the climb at your target cadence.

Combination	Ratio
34/28	1.21
34/32	1.06
34/34	1.00
33/36	0.92
30/36	0.83
40/44	0.91
38/52	0.73

What gear ratio means

The gear ratio is front teeth divided by rear teeth. 34/34 gives 1.0: one crank turn turns the rear wheel exactly once. With 28 mm tires on 700C that is about 2.13 m per crank turn, called development. Smaller values are easier: you cover less ground per turn but need less force.

Why the steepest section counts

At the same power you are slowest on the steepest section. That is where it is decided whether your easiest gear is low enough. The average of a climb says little if there is a 15% ramp in between. That is why the calculator asks for both: the steepest section for the gear, average and length for the duration.

Power and weight

On a steep climb you are so slow that air resistance hardly matters. Speed then depends almost only on power relative to total weight. Weigh 10% more and you need a correspondingly easier gear at the same power. Luggage counts just like rider weight.

Example from the chart: at 84 kg and 200 watts you climb 10% at about 8.1 km/h and need 0.79. With 250 watts 0.98 is enough.

Smaller chainring or bigger cassette

For the easiest gear only the ratio counts. 32/32 is as easy as 34/34. A smaller chainring also makes the hardest gear easier, though. A bigger cassette keeps the hard gear but widens the gaps between gears and often needs a different derailleur.

Derailleur and capacity

Every rear derailleur has a largest cog it can reach and a capacity. Capacity is the sum of the tooth difference front and rear, meaning how much chain the cage has to take up. If you fit a bigger cassette or different chainrings, check both. The gear calculator does and only suggests combinations with a matching derailleur. It does not check freehub, chain or shifters.

Assumptions and limits

The calculation uses rolling resistance 0.004, drag area 0.40 m², drivetrain efficiency 97%, no wind and steady power. On gravel, into a headwind or if you fade on ramps you need an easier gear than in the chart. Treat the values as a guide.