If you have ever tried to compare two bikes, or work out whether a new cassette will give you an easier climbing gear, you will quickly bump into three overlapping ideas: gear ratio, gear inches, and development (sometimes called metres of development or roll-out). They all describe the same underlying thing — how far the bike travels for one turn of the pedals — but they express it in different units, and each is useful in a different situation. Once you understand how the three relate, comparing gears across bikes, wheel sizes and drivetrains becomes straightforward. This guide explains each measure, walks through worked examples, and shows how to get instant answers using the gearing converter on the Convert.bike home page.

Gear ratio: the simplest measure

The gear ratio is the most basic number, and everything else is built on top of it. It is simply the number of teeth on the chainring (the front ring the chain sits on) divided by the number of teeth on the rear cog you have selected:

  • Gear ratio = chainring teeth ÷ cog teeth

So a 50-tooth chainring paired with a 14-tooth cog gives a ratio of 50 ÷ 14 = 3.57. That means for every single turn of the cranks, the rear wheel rotates 3.57 times. A bigger ratio is a "harder" or "taller" gear (more wheel turns per pedal stroke, good for speed); a smaller ratio is an "easier" or "lower" gear (fewer wheel turns, good for climbing).

Ratios are quick to calculate in your head and great for comparing two gears on the same bike. A 50×11 (4.55) is clearly taller than a 50×14 (3.57). But the ratio alone has a blind spot: it ignores wheel size. A ratio of 3.57 on a 700c road wheel covers far more ground than the same ratio on a small 20-inch folding-bike wheel, because the wheel that actually meets the road is bigger. That is exactly why gear inches and development exist. For a deeper walkthrough of the arithmetic, see our dedicated guide on how to calculate gear ratio.

Gear inches: bringing wheel size in

Gear inches is an old but wonderfully practical unit that folds wheel size into the ratio. It dates back to penny-farthing days, when a bike was described by the diameter of its (single, direct-drive) front wheel. Gear inches answers the question: "what size of direct-drive wheel would behave like this gear?" The formula is:

  • Gear inches = gear ratio × wheel diameter in inches

For a standard 700c wheel, the effective diameter (rim plus tyre) is roughly 27 inches, so a handy shortcut is gear inches ≈ ratio × 27. Taking our 50×14 example again: 3.57 × 27 ≈ 96 gear inches. That is a typical fast-cruising road gear.

The beauty of gear inches is that it lets you compare gears across completely different bikes on one scale. A mountain bike's lowest climbing gear might be around 18–22 gear inches, a relaxed touring gear around 30–40, an all-round road gear around 60–80, and a flat-out sprint gear well over 100. Because wheel size is baked in, a 26-inch mountain bike and a 700c road bike can be put side by side honestly. To understand how the underlying wheel diameters differ, our guide to understanding bike wheel sizes is a useful companion.

Development: how far you actually travel

Development (often metres of development, or roll-out) is the most physically intuitive of the three. It tells you how many metres the bike rolls forward for one complete turn of the cranks. The formula multiplies the wheel circumference by the gear ratio:

  • Development (m) = wheel circumference (m) × gear ratio

A 700c wheel has a circumference of roughly 2.1 metres. So our 50×14 gear develops 2.1 × 3.57 ≈ 7.5 metres per pedal revolution. In other words, one smooth turn of the cranks carries you about seven and a half metres down the road. Drop into an easy 34×28 climbing gear (ratio 1.21) and development falls to 2.1 × 1.21 ≈ 2.5 metres per revolution — you spin much faster to cover the same ground, which is exactly what you want when the road tilts upward.

Development is especially loved by track riders and fixed-gear cyclists, who often talk in terms of "rolling out" a gear by literally measuring how far the bike moves for one crank turn. It is also the cleanest way to connect gearing to speed, because once you know metres per revolution you only need cadence to get velocity — more on that below.

The three measures side by side

Using the same 50×14 on a 700c wheel, here is how the numbers line up:

  • Ratio: 3.57 (pure number, no units)
  • Gear inches: ≈ 96 in (ratio × 27)
  • Development: ≈ 7.5 m per crank revolution (circumference × ratio)

They are three views of one reality. Ratio is fastest for same-bike comparisons, gear inches is the universal scale for comparing different bikes, and development is the most tangible for picturing distance and linking to speed.

Comparing gears across wheel sizes

This is where ratio alone trips people up. Suppose you ride a 26-inch wheel (559 mm bead-seat diameter, roughly 26 inches overall) and a friend rides 700c (622 mm, roughly 27.3 inches). You both run a 2.0 ratio. Your gear inches are about 2.0 × 26 = 52, while your friend's are 2.0 × 27.3 ≈ 55. Same ratio, meaningfully different gears — your friend travels further per pedal stroke despite identical sprockets. If you want to truly match a gear when changing wheel size, hold gear inches (or development) constant, not ratio. To do that you adjust the cog or chainring to compensate for the new wheel diameter. The home-page converter handles this conversion for you, so you don't have to redo the arithmetic each time.

Typical gear ranges

Knowing what "good" looks like helps you judge whether a setup suits your riding:

  • Very low climbing gears: roughly 18–26 gear inches (around 1.5–2.0 m development). Common on mountain bikes and loaded tourers for steep, slow climbs.
  • All-round gears: roughly 50–75 gear inches (around 4–6 m). Comfortable cruising on the flat at a moderate cadence.
  • High speed gears: roughly 90–120+ gear inches (around 7–9.5 m). For descending and sprinting, where you want lots of ground per stroke.

A wide-range drivetrain simply means a big gap between the lowest and highest of these — handy for varied terrain, at the cost of bigger jumps between gears.

From gearing to speed

Because development is metres-per-revolution, speed follows immediately once you add cadence (pedal revolutions per minute). Distance per minute = development × cadence, and km/h = that figure × 60 ÷ 1000. At a steady 90 rpm in our 50×14 (7.5 m development): 7.5 × 90 = 675 m/min, × 60 ÷ 1000 = 40.5 km/h. This link between gearing, cadence and velocity is explored fully in our bike speed, cadence and gearing guide.

Using the Convert.bike gearing converter

Rather than reaching for a calculator, the gearing tool on the Convert.bike home page lets you enter your chainring teeth, cog teeth and wheel size, and instantly returns the ratio, gear inches and development together. That makes it easy to experiment: try a different cassette, switch wheel sizes, or line up two gears to see exactly how a change alters how far you travel per stroke. Because all three measures appear at once, you can pick whichever language suits the comparison you are making.

Next steps

Start by working out the gear inches and development of your current setup so you have a baseline, then compare your lowest and highest gears to understand your real range. If you are thinking of changing wheels or a cassette, hold gear inches constant to keep the feel you like. Pop your numbers into the home-page gearing converter to confirm the maths, then read how to calculate gear ratio for the fundamentals and understanding bike wheel sizes to see how wheel diameter shapes every one of these numbers.