Hobbies · Cycling
Cycling climb time saved per kg.
Enter total mass, climbing power, gradient and ascent. The calculator solves the power balance for your steady climbing speed, gives the climb time, and repeats it with less mass to show the time saved. Example: 80 kg total at 250 W on a 7% gradient for 500 m of ascent takes 30 min 8 s at 14.3 km/h. Taking 1 kg off saves 19.2 seconds, and 5 kg saves 95.4 seconds, at the same power.
Your numbers
Result
Working out the result.
How the climb time is calculated
Wikipedia's “Bicycle performance” article gives the power equations. Gravity: PS = v m g sin(arctan s) ≈ v m g s. Rolling resistance: PR ≈ v m g Crr. Air drag in still air: PD = ½ ρ v³ CDA. The rider's pedal power covers all three after drivetrain losses: P = (PD + PR + PS) ÷ η. The article quotes ρ of about 1.225 kg/m³ at sea level and 15°C, Crr of 0.003 to 0.006 at low speed, g of 9.8 m/s², and derailleur losses of 1 to 7%.
This page solves that balance for the steady speed by bisection, using the exact sin and cos of the slope angle, then divides the distance climbed by that speed. It assumes no wind, constant gradient, constant power and no acceleration. The default drag area of 0.35 m² and rolling resistance of 0.004 are our choices inside the quoted ranges; change them for your bike.
Worked examples with real numbers
- The reference point. The same article says 90 kg at 175 W on a 7% grade needs about 2.6 m/s, and 65 kg at 285 W about 5.3 m/s. With 97% efficiency, Crr 0.004 and a drag area of 0.30 m² (our choices, as the article gives none) the solver returns 2.6, 4.3, 3.3 and 5.3 m/s for its four examples, which is how we checked it. The default drag area on this page is 0.35 m², so your figures will be slightly lower.
- Your 80 kg, 250 W, 7%, 500 m example. 7,160 m of road at 4 m/s takes 30 min 8 s.
- One kilogram. At 79 kg the climb takes 29 min 49 s, a saving of 19.2 seconds, about 1.1% of the time.
- Published rule of thumb. Wikipedia says removing 1 kg adds 0.04 m/s on a 7% grade for a 90 kg system and 0.07 m/s for a 65 kg one, and that over a one-hour climb saving 453 g gains about 69 m for the heavier system and 107 m for the lighter one.
What this calculator leaves out
It does not model wind, changing gradient, surging, descending, altitude or heat. Power is held fixed, which flatters weight loss: real riders who lose mass often lose some power too. It also treats the saving as proportional to climb length, so a longer climb saves proportionally more seconds. The Wikipedia article itself notes the small-slope approximation overstates the gravity term by about 6% at a 0.35 slope; this page uses the exact angle.
Common mix-ups
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Often assumedCutting weight helps a climb only slightly, so it is not worth thinking about.
What the source saysThe article says that on a climb, cutting total system weight by 10% saves nearly 10% of the power needed. Per kilogram the effect is small, 0.04 m/s on a 7% grade for a 90 kg system, but it adds up over a long climb: about 69 m gained over one hour for 453 g. [1]
Checked against these sources on .
Frequently asked questions
How much time does losing 1 kg save on a climb?
With 80 kg total, 250 W and a 7% gradient, 1 kg saves about 19.2 seconds over a 500 m climb, roughly 1.1% of the time. The saving grows with climb length and shrinks as the gradient gets shallower.
Does the weight of the bike count the same as the rider?
Yes. Gravity acts on total mass, so a kilogram off the bike is a kilogram off the rider. Enter rider, bike, clothing and bottles together.
Why does this need my power?
Climb time depends on how hard you can go. The calculator holds your power fixed and lets speed rise when mass falls. If you lose mass and power together, the benefit shrinks.
Where do the equations come from?
From Wikipedia’s Bicycle performance article, which gives the power terms for gravity, rolling resistance and air drag. The page’s worked examples were reproduced as a check.
Why is my drag area CdA my own number?
The source gives no typical CdA for a rider, so the default of 0.35 m² is our assumption for an upright position. On steep climbs speed is low and drag matters little, so the result is not very sensitive to it.
Sources
Retrieved
- Wikipedia: Bicycle performance — the power equations, constants, 7% worked examples and the per-kilogram and 453 g figures (read 2026-10-26)
A steady-state model, not a race prediction
Not affiliated with Wikipedia. The article was read on 26 October 2026 and can change. The model assumes no wind and constant power and gradient. Nothing you type is sent or stored.