Cycling Power-to-Weight Ratio Calculator
Calculate watts per kilogram from FTP and body weight, compare against category benchmarks, and see what climbing performance the ratio implies.
🚴 Exercise Science📐 W/kg = FTP (watts) / body weight (kg)🏥 Health
Weight units
FTP (watts)
Body weight
Sex
Climb gradient for estimate (%)
Please enter valid values.
Formula & Reference
| Variable | Symbol | Formula | Units |
|---|---|---|---|
| Cycling Power-to-Weight Ratio Calculator | — | W/kg = FTP (watts) / body weight (kg) | watts per kg |
Step-by-Step Examples
Example 1
Recreational Rider
FTP 220 W at 78 kg, male.
- W/kg = 220 / 78
- W/kg = 2.82
- Falls in the recreational band
✓ 2.82 W/kg — recreational
Example 2
Trained Rider
FTP 300 W at 72 kg, male.
- W/kg = 300 / 72
- W/kg = 4.17
- Well-trained band, roughly Cat 3 equivalent
✓ 4.17 W/kg — well trained
Example 3
Weight vs Power Trade-Off
FTP 280 W at 75 kg versus 266 W at 70 kg.
- First: 280 / 75 = 3.73 W/kg
- Second: 266 / 70 = 3.80 W/kg
- Losing 5 kg while giving up 14 W still improves the ratio
- But on flat terrain, the rider with 280 W absolute is faster
✓ Ratio improves, absolute power falls
Real-World Applications
Climbing Performance
On sustained climbs, power-to-weight is the dominant determinant of speed, since most resistance is gravitational.
Category Benchmarking
W/kg is the standard way riders compare fitness across different body sizes and is used in virtual racing categories.
Flat vs Hilly
On flat terrain aerodynamic drag dominates, so absolute watts matter more than the ratio.
Two Levers
The ratio improves through raising power or lowering weight, but the two interact and are not independent.
Common Mistakes to Avoid
⚠️
Pursuing weight loss at the expense of power
Aggressive weight loss typically reduces FTP as well. The ratio can worsen if power falls faster than weight, and health consequences can be serious.
⚠️
Comparing W/kg across durations
FTP-based W/kg is not comparable to a 5-minute or 1-minute figure. Power duration curves differ substantially between riders.
⚠️
Ignoring how FTP was measured
A 20-minute test with a 95% adjustment, a ramp test, and a full 60-minute effort produce different numbers. Comparisons need a consistent protocol.
Frequently Asked Questions
What is a good power-to-weight ratio? ▾
It depends on the rider. Recreational cyclists commonly sit around 2.5 to 3.5 W/kg at FTP, trained amateurs 3.5 to 4.5, and elite professionals above 5.5.
Why does W/kg matter for climbing? ▾
On a steep climb most of the power output goes into lifting body and bike against gravity, so speed scales closely with power per kilogram.
Should I focus on losing weight or gaining power? ▾
For most riders, raising power is the healthier and more sustainable route. Weight loss below a healthy range tends to reduce power and carries real health costs.
What is FTP? ▾
Functional threshold power — the highest power output sustainable in a quasi-steady state, conventionally for about an hour.
Does W/kg matter on flat terrain? ▾
Much less. On the flat, aerodynamic drag dominates and absolute power output is the better predictor of speed.