Bicycle Speed Calculator

30 km in 1 hour 12 minutes is an average of 25.0 km/h

Average cycling speed is the distance you rode divided by the time it took. Cover 30 km in 1 hour 12 minutes, which is 1.2 hours, and you averaged 30 ÷ 1.2 = 25.0 km/h (about 15.5 mph), or 2 minutes 24 seconds per kilometre. Turn the same formula around and distance ÷ speed gives the ride time, while speed × time gives the distance. The calculator above asks which of the three you want and only needs the other two.

Speed alone does not tell you how hard the ride is. Add your weight, bike weight, riding position, surface, gradient and wind, and the calculator shows the pedal power needed to hold that speed, split into air drag, rolling resistance, climbing and drivetrain loss, along with an estimate of calories burned. A 70 kg rider on a 10 kg bike, hands on the hoods, rolling along flat asphalt at 25 km/h with no wind, needs about 99 W. If you have a power meter, enter its reading under speed from power to see the average speed it buys you in today's conditions, then use the gear section to find which gear and cadence deliver that speed.

Why work it out, and when it helps

• Planning a commute: a 12 km route at 18 km/h takes 40 minutes. Door-to-door averages that include traffic lights are lower than the moving average on a bike computer, so work out your real average from a past trip and the next estimate will be closer.
• Planning a long ride: 100 km at an average of 25 km/h takes 4 hours, but on a 3% climb the same power cuts your speed almost in half. The gradient comparison lets you time each section and plan food stops and your return.
• Choosing gears: to ride 25 km/h on the flat in 50 × 17 you only need 67 rpm, while 34 × 17 asks for 99 rpm. Follow the row for your usual cadence in the gear chart and the right gear stands out.
• Reading power meter numbers: knowing that 150 W is 29.5 km/h on the flat but only 21.1 km/h into a 15 km/h headwind lets you compare rides fairly, even when conditions differ.
• Riding an e-bike: in the EU and UK, motor assistance cuts out at 25 km/h (see common mistakes below). Checking what your own legs must produce above that speed helps you split the effort between battery and body.

How the calculation works

1. Pick what to solve for: average speed (enter distance and time), ride time (distance and speed), distance (time and speed) or speed from power (pedal power, distance optional). Everything is computed in kilometres and seconds; only the displayed values are rounded.
2. Three formulas: speed (km/h) = distance (km) ÷ time (h), time = distance ÷ speed, distance = speed × time. Time per km is 3,600 ÷ speed in seconds, m/s is km/h ÷ 3.6 and mph is km/h ÷ 1.609344.
3. Required power: the calculator uses the road cycling power model of Martin and colleagues (1998). Power at the wheel = (air drag + rolling resistance + gravity) × ground speed. Air drag = ½ × air density 1.225 kg/m³ × CdA × (speed + headwind)², rolling resistance = Crr × total mass × 9.80665 × cos θ, and gravity = total mass × 9.80665 × sin θ, where θ = atan(gradient % ÷ 100). Pedal power is wheel power divided by a drivetrain efficiency of 97.6%. Each position sets a typical CdA (drag area in m²) and each surface a typical Crr (rolling resistance coefficient). Wheel inertia, acceleration and braking are left out.
4. Speed from power: because power rises with the cube of speed, the equation cannot be solved for speed directly. The calculator searches numerically between 0 and 180 km/h for the speed at which pedal power equals your target. When a descent or strong tailwind keeps you moving without pedalling, the required power is shown as 0 and the speed you would coast at is shown instead.
5. Calories: pedal work (kJ) = power (W) × time (s) ÷ 1000. Human muscle is roughly 24% efficient (18–26%) and 1 kcal = 4.184 kJ, so kJ ÷ 4.184 ÷ 0.24 ≈ kJ × 1.0. In other words, kcal burned roughly equals kJ of pedal work. Because this is gross efficiency, the figure is a rough total for the ride that already includes resting metabolism.
6. Gears and cadence: gear ratio = chainring teeth ÷ sprocket teeth, development (m) = ratio × wheel circumference (mm) ÷ 1000, gear inches = ratio × circumference ÷ π ÷ 25.4, and speed (km/h) = cadence (rpm) × development × 60 ÷ 1000. Circumferences come from the CatEye tyre circumference chart (2015); for a size that is not listed, estimate it with the ISO formula π × (bead seat diameter + 2 × tyre width) and type it into the custom field.

Base case: the tables and examples below assume a 70 kg rider plus 10 kg of bike and luggage, hands on the hoods, asphalt, flat road and no wind. Change any condition in the calculator and the figures change with it.

Average speed and required power by distance and time

Required power climbs steeply with speed because the power spent on air drag grows with the cube of speed. The 99 W needed at 25 km/h becomes 337 W at 40 km/h, 3.4 times as much, and air drag accounts for 85% of it. At commuting speeds of 18–20 km/h, by contrast, around 50 W is enough, which is easy to sustain for a long time.

Gear chart: 50/34T × 11-28T, 90 rpm, 700×25C

A gear chart shows the theoretical speed each gear gives at the same cadence. The chart below uses the most common road setup, a compact crankset (50/34T) with an 11-28T cassette and 700×25C tyres (2,105 mm circumference), pedalled at 90 rpm. The chart in the calculator redraws for whatever setup you enter and highlights the gear you are using.

The biggest gear, 50 × 11 (ratio 4.55), gives 51.7 km/h at 90 rpm, while the smallest, 34 × 28 (ratio 1.21), gives 13.8 km/h, a 3.7-fold spread. Cruising at 25 km/h on the flat takes about 67 rpm in 50 × 17 or 87 rpm in 34 × 15, so riders who like 80–100 rpm usually shift a sprocket or two to land in their comfort zone.

The same 150 W with a different position, surface, gradient or wind

Suppose you hold a steady 150 W on a power meter. This table shows the average speed and the time for 30 km when one thing at a time changes from the base case.

On the flat, position is what separates riders. On a 6% climb air drag shrinks to a small share, so total mass matters more than how aero you are. Wind enters through the square of speed plus headwind, not ground speed, which is why a 15 km/h headwind costs about 8 km/h while a tailwind of the same strength adds only about 10 km/h on the way back. An out-and-back ride in the wind therefore averages slower than the same ride on a calm day.

Common mistakes

• Mixing up moving and overall average: the average speed on most bike computers and apps leaves out stopped time. Distance divided by the full start-to-finish time is lower, so use the full time when you need to arrive somewhere on schedule.
• Entering wheel diameter instead of circumference: development and speed depend on circumference, the distance covered in one wheel turn. A 700C wheel is about 2.1 m around but only 0.67 m across. A circumference that is 1% off makes the speed 1% off too.
• Treating gear inches and development as the same thing: gear inches is a traditional unit describing the diameter of a wheel that would go as far if the pedals were attached to it directly, as on a penny-farthing. Development is the distance travelled per crank revolution, in metres. Both describe how big a gear is, but the numbers differ.
• Confusing cadence with wheel speed: cadence is how many times the cranks turn per minute. Wheel revolutions are cadence multiplied by the gear ratio.
• Entering gradient as an angle: gradient in % is the rise in metres per 100 m of horizontal distance. 3% is about 1.7° and 10% about 5.7°. The average gradient a route app shows smooths over steeper ramps, so a climb can feel harder than its number suggests.
• Entering a crosswind as a headwind: the calculator only takes the wind component along your direction of travel. If you do not know the angle of a side wind, compare with the wind set to 0.
• Forgetting the e-bike assist limit: in the EU, Regulation (EU) No 168/2013, Article 2(2)(h), covers pedal-assisted bikes whose motor is rated at 250 W or less and whose assistance tapers off and cuts out before 25 km/h and when you stop pedalling. In Great Britain, an electrically assisted pedal cycle must not be motor-driven above 15.5 mph (about 25 km/h). In the US, the federal definition of a low-speed electric bicycle (15 U.S.C. 2085) is a motor under 750 W with a top speed under 20 mph on motor power alone, and states add their own rules. The speedometer line marks the EU 25 km/h limit; above it, calculate with the power you can produce yourself.

Limits and cautions

• Required power and speed from power are model values for steady riding. Accelerating away from lights, cornering, drafting behind another rider, tyre pressure, wet roads and clothing are not included. Differences of 10–20% from a power meter are common.
• The CdA for each position and the Crr for each surface are typical values. The 0.32 m² for the drops is the midpoint of wind tunnel measurements (Nonweiler 1956: 0.311 m²; Barry and colleagues 2015: 0.325 m²). The hoods 0.34, upright 0.40, aero bars 0.27 and upright MTB 0.50 are assumptions scaled from that reference. Asphalt at 0.005 is the top end of roller measurements for high-pressure road tyres (0.0022–0.0050), and concrete 0.006, gravel 0.012 and dirt 0.020 are assumptions. Build, clothing, wheels and helmet can shift CdA by 0.05 m² or more in the same position, and tyres and pressure can nearly double Crr. If you know your own values, switch position or surface to custom and enter them.
• Air density is fixed at 1.225 kg/m³, the sea-level value at 15 °C. At altitude or on hot days the air is thinner and the same power goes a little faster; on cold days the opposite is true.
• Calories are a rough estimate assuming 24% muscle efficiency and are a rough total for the ride (gross efficiency includes resting metabolism) and ignore heat lost to wind and cold. Use them to compare rides rather than to plan a diet or weight loss.
• Gear chart speeds are theoretical. Heavily cross-chained combinations (big ring with big sprocket, small with small) wear the drivetrain and waste power, so riders avoid them in practice.
• Your inputs are not sent to a server; they are only added to the address when you copy a link. Do not adjust the calculator while riding. Stop somewhere safe first.

Sources

• 01Martin JC, Milliken DL, Cobb JE, McFadden KL, Coggan AR. Validation of a Mathematical Model for Road Cycling Power. J Appl Biomech 14(3):276–291, 1998Power model built from air drag, rolling resistance, gravity and drivetrain loss; standard error against measured power 2.7 W (PMID 28121252)
• 02Malizia F, Blocken B. Bicycle aerodynamics: History, state-of-the-art and future perspectives. J Wind Eng Ind Aerodyn 200:104134, 2020Table 2 wind tunnel data for the drops (Nonweiler 1956 A 0.334 m², k 0.571; Barry et al. 2015 A 0.472 m², k 0.422; CdA 0.31–0.33 m²), Table 1 rolling resistance (Wilson 2004 mean 0.008; Bourlet 1894 road 0.009, track 0.004), Kyle 1989 clip-on bars 13.7–15.5% reduction
• 03CatEye: Tire Circumference Chart (2015-11-06, PDF)700×23C 2,096 mm, 25C 2,105, 28C 2,136, 32C 2,155, 38C 2,180, 29×2.1 2,288, 27.5×2.1 2,148, 26×1.95 2,050, 20×1.75 1,515, 16×1.5 1,185 mm
• 04Regulation (EU) No 168/2013 on the approval and market surveillance of two- or three-wheel vehicles and quadricycles — EUR-LexArticle 2(2)(h): pedal-assisted cycles with a motor of 250 W or less, assistance cut off before 25 km/h and when pedalling stops, are outside the scope
• 05Electric bikes: licensing, insurance, VAT and tax — GOV.UKElectrically assisted pedal cycle: continuous rated power no more than 250 W, no motor propulsion above 15.5 mph, rider 14 or over
• 0615 U.S.C. 2085 Low-speed electric bicycles — Cornell Law School LIIMotor under 750 W, top speed under 20 mph on motor power alone with a 170 lb rider
• 07ISO 2533:1975 Standard AtmosphereAir density at sea level and 15 °C: 1.225 kg/m³
• 08Rolling resistance — rolling resistance coefficient examplesRoller-measured Crr for high-pressure bicycle tyres 0.0022–0.0050 (citing biketechreview data)
• 09Bicycle performance — energy efficiency, drivetrainMuscle efficiency 18–26%, chain drive losses 1–7% (citing Wilson & Papadopoulos, Bicycling Science)
• 10Crouch TN, Burton D, LaBry ZA, Blair KB. Riding against the wind: a review of competition cycling aerodynamics. Sports Engineering 20:81–110, 2017Table 4 wind-tunnel drag areas: upright (stem/hoods) 0.27–0.36 m², dropped 0.24–0.33 m², time trial 0.21–0.30 m²; the drops cut drag by 15–20% versus upright
• 11TrainingPeaks: Predicting and Measuring KilojoulesCyclists are 20–25% efficient, so kJ at the pedals and kcal burned are roughly 1:1

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