Bike Gear Calculator - Chainring, Cog, Gear Inches
Use the bike gear calculator to enter the actual chainrings and cogs on your drivetrain and read off gear ratios, gear inches, and a full chainring-by-cog table.
Bike Gear Calculator
Results
Gear ratio table (chainring by cog)
Gear inches table (chainring by cog)
What Is the Bike Gear Calculator?
A bike gear calculator turns the chainrings and cogs on your drivetrain into a printable gearing table so you can compare every ratio before you buy parts. This calculator accepts the tooth counts on your chainrings and cassette, pairs each chainring with each cog, and prints two tables in gear ratio and gear inches on the wheel you ride.
- • Road cyclists: Compare a 50/34 compact against a 53/39 standard on the same 11-32 cassette to see the 22 ratios in each table.
- • Mountain bikers planning a 1x drivetrain: Enter a 32 tooth chainring with an 11-50 cassette on a 29er wheel to see the 12 combinations that decide whether you can clean technical climbs.
- • Touring and gravel riders: Try a 46/30 sub-compact with a 11-36 cassette and read the lowest and highest gear inches for loaded climbs and fast descents.
If you already know the chainring and cog you ride, the Bicycle Gear Ratio Calculator takes one chainring, one cog, and a wheel size and returns the gear ratio, gear inches, and speed at a chosen cadence.
How the Bike Gear Calculator Works
The calculator walks every chainring in your list against every rear cog in your list and writes the resulting gear ratio and gear inches into a two-way table. Each cell is independent, so changing the wheel rescales the entire gear inch column in real time.
- chainrings: Comma-separated tooth counts for every chainring on the crank, in any order.
- cogs: Comma-separated tooth counts for every cog on the cassette, typically smallest to largest.
- wheelDiameter: Outside wheel diameter in inches including the inflated tire.
If you ride a single chainring, enter that one number in the chainrings field and the table collapses to one row per cog. Duplicates inside either list are ignored, so 50, 50, 34 prints the same table as 50, 34.
Road compact double 50/34 with 11-32 cassette on 700c
Chainrings 50, 34 teeth. Cogs 11, 12, 13, 14, 15, 17, 19, 21, 24, 27, 32 teeth. Wheel 28 in.
22 combinations. Easiest gear 34x32 = 1.06 ratio, 30 gear inches. Hardest gear 50x11 = 4.55 ratio, 127 gear inches.
Ratio range 1.06 to 4.55 and gear inches 30 to 127 on a 700c road wheel.
That covers seated climbing near 4 mph up to about 35 mph on the flat at 90 RPM.
According to Sheldon Brown gear calculator reference, gear inches are wheel diameter in inches times chainring teeth divided by rear cog teeth, rounded to the nearest whole number for the printed gearing table.
Once you pick a row from the gearing table, the Bike Cadence Calculator takes that chainring, cog, and wheel size and turns the gear ratio into a real-world pedal RPM or speed at your cadence.
Key Concepts Explained
Four ideas come up every time cyclists read a gearing table, worth understanding before you treat the calculator's numbers as gospel.
Gear ratio
Chainring teeth divided by rear cog teeth. Above 1.0 the wheel turns faster than the pedals; below 1.0 it turns slower.
Gear inches
A gear ratio scaled by the wheel diameter in inches. A 50x11 on a 700c wheel reads about 127 gear inches.
Chainring range
The spread between the smallest and largest chainring tooth counts. Wider covers more climbing and top speed.
Cassette range
The spread between the smallest and largest cog tooth counts. A wider cassette fills the gaps left by a narrow chainring range.
These four ideas work together: gear ratio is the mechanical truth, gear inches is the felt truth, and the chainring and cassette ranges decide which ratios are available.
The Cycling Power-to-Weight Ratio Calculator translates your FTP and body weight into a W/kg ratio that decides whether the bottom of the gearing table clears your steepest climbs.
How to Use This Calculator
The calculator mirrors the order a mechanic works through when sizing a new drivetrain: list the chainrings, list the cogs, set the wheel size, then read the table.
- 1 Enter the chainrings: Type the chainring tooth counts as a comma-separated list. For 1x, enter the single chainring number.
- 2 Enter the cassette cogs: Type the cog tooth counts as a comma-separated list, usually smallest to largest. These are stamped on the cassette body.
- 3 Enter the wheel diameter: Measure an inflated wheel with the tire, in inches. 28 is 700c, 29 a 29er, 27.5 a mid-size mountain wheel.
- 4 Read the summary numbers: Total combinations, easiest and hardest gear ratios, the matching gear inches, and the pair closest to a 1:1 ratio.
- 5 Scan the gear ratio table: Compare the combinations and look for ratios within 5 percent of each other to spot duplicate gears.
- 6 Scan the gear inches table: Translate each ratio into a real wheel size and check your lowest gear inches against the steepest climb you plan to ride.
Practical example. Enter chainrings 50, 34, cogs 11, 12, 13, 14, 15, 17, 19, 21, 24, 27, 32, wheel 28. The table shows 22 combinations, 30 gear inches at the bottom, and 127 at the top.
Once the gearing table is in front of you, the Cycling FTP Calculator converts a recent 20-minute or 8-minute test into an FTP that tells you whether your gear range is realistic at the cadence you hold.
Benefits of Using This Calculator
These benefits show up most clearly when used as a planning tool before a parts order.
- • Compare real drivetrains before you buy: Enter the chainrings and cogs for a 50/34 with 11-32 and a 53/39 with 11-28 to see the 22 combinations in each table.
- • Spot duplicate gears: The table highlights combinations within 5 percent of each other, so you can see when a 2x setup duplicates a ratio pair.
- • Match gearing to wheel size: Re-enter the chainrings and cogs on 700c, 27.5, and 29er wheels to predict road, gravel, and mountain feel.
- • Plan a 1x conversion: Enter one chainring with your existing cassette and confirm the lowest gear is easy enough for your steepest climb.
- • Brief a mechanic or co-rider: Share the printed gearing table so the chainrings and cogs you have in mind are clear, instead of guessing from group set names.
After you lock in a gearing table, the Calories Burned Biking Calculator turns the speed each ratio produces at your cadence into an estimated calorie burn for the ride.
Factors That Affect Your Bike Gear Calculator Result
Five factors drive the gearing table, and understanding them helps you decide when the numbers match what you feel on the bike.
Wheel diameter accuracy
A 1 inch error on a 700c wheel shifts every gear inch in the table by about 3.6 percent.
Cassette step spacing
Even tooth steps across a cassette, such as 11-12-13-14, create even percentage jumps in the table, while a wider jump such as 11 to 13 leaves a noticeable gap.
Chainring spread
A wide spread such as 46-30 doubles the low end without changing the cassette, but it also leaves a larger jump in the middle of the table that a 50-34 would not.
Drivetrain overlap
A single chainring loses the half-step overlap of a double, so a 1x build often shows bigger jumps in ratios between two cogs than a 2x build would have spanned.
Tire size and pressure
Tire size and pressure change the effective wheel diameter between a race day and a loaded tour.
- • Internal hub gears and continuously variable transmissions are not represented, so the table fits only derailleur drivetrains.
- • Cross-chained combinations are listed only for completeness; the chain runs at an extreme angle in practice.
- • Wheel and tire diameter vary by manufacturer and inflation, so a single wheel input cannot capture every real-world rolling diameter.
According to Wikipedia bicycle wheel reference, the standard 700c road wheel has an outside diameter near 28 inches once an inflated tire is included.
According to Wikipedia gear ratio reference, the bicycle gear ratio is chainring teeth divided by rear cog teeth.
Triathletes can pair the result with the Triathlon Finish Time Calculator to estimate total race time.
Frequently Asked Questions
Q: What is a bike gear calculator?
A: A bike gear calculator takes the actual tooth counts on your chainrings and cassette cogs and prints a chainring-by-cog table of gear ratios and gear inches. It lets cyclists compare a real drivetrain, such as a 50/34 with an 11-32, before buying parts.
Q: How do you calculate bike gear ratio?
A: Divide the number of teeth on the front chainring by the number of teeth on the rear cog. A 50 tooth chainring with a 12 tooth cog returns 4.17, and the same chainring with a 25 tooth cog returns 2.0.
Q: What are gear inches on a bicycle?
A: Gear inches are the gear ratio multiplied by the wheel diameter in inches, rounded to the nearest whole number. A 50x11 on a 700c wheel reads about 127 gear inches.
Q: How do I choose the right chainring and cassette?
A: Pick chainrings that cover your average cruising cadence, and a cassette that adds enough low end for your steepest climb. The gear inches column tells you whether the lowest gear is easy enough for a 15 to 20 percent grade.
Q: Is gear ratio the same as gear inches?
A: No. Gear ratio is a unitless ratio of chainring teeth to cog teeth, while gear inches scale that ratio by the wheel diameter.
Q: How many gears does my bike need?
A: Most riders do well with about 7 to 8 ratios of lowest to highest, roughly a 22 to 30 gear inch climbing gear paired with a 90 to 130 gear inch top gear.