Cycling Power-to-Weight: Watts per Kilogram, FTP, and How Fast You Climb

The Physics

The power needed to climb is mostly the rate at which you raise your mass against gravity: P = m × g × v_vertical, plus smaller terms for air and rolling resistance. Dividing by mass gives P/m = g × v_vertical, so vertical speed = (W/kg) ÷ 9.81 m/s. At 3.57 W/kg, the ideal vertical speed is 0.364 m/s, or 1,310 meters per hour. Real-world losses from drag, rolling resistance, and drivetrain friction reduce this to roughly 80% to 90% on steady climbs of 6% or more. On shallower slopes, air resistance matters more and mass matters less.

This simple model explains why lighter riders do well in the mountains and heavier riders do better on flat roads, where absolute power and aerodynamics dominate.

Example: Climbing a Mountain Pass

A climb of 1,000 meters of elevation gain would take 1,000 ÷ 1,114 = 0.9 hours (54 minutes) for the 3.57 W/kg rider, and 1,000 ÷ 668 = 1.5 hours for the 2.14 W/kg rider. Professional climbers sustain 6 W/kg or more for 30 to 60 minutes, for climbing rates around 1,800 to 1,900 meters per hour. The calculation also shows the benefit of losing weight: dropping from 70 kg to 67 kg at the same 250 W raises the ratio to 3.73 W/kg, or about 4.5% faster. Carrying a 3 kg bottle and gear has a similar effect in reverse: bike and kit weight count along with body weight in total mass, so the real effect is smaller, about 3%.

Measuring FTP

A common field test is a 20-minute all-out effort after a thorough warm-up, with FTP estimated as 95% of the average power: if you average 263 watts, your FTP is about 250 watts. Ramp tests on indoor trainers give estimates from the final stage reached. Power meters measure watts at the pedals or crank; heart rate and perceived exertion are less precise. Retest every 6 to 8 weeks to track progress. Training zones are set as percentages of FTP, from active recovery (below 55%) to endurance (56% to 75%), tempo (76% to 90%), threshold (91% to 105%), and VO₂max intervals (106% to 120%).

Improving Power-to-Weight

Raise power through structured training: base endurance miles, threshold and VO₂max intervals, and strength work, with enough recovery. Reduce excess body fat gradually, with moderate calorie deficits, high protein, and adequate fuel on the bike, since aggressive weight loss reduces power. A rider who raises FTP by 10% and drops body weight by 5% improves the ratio by 15.8%. Equipment contributes less: each kilogram saved on the bike matters about as much as a kilogram of body weight, but at a much higher cost per gram.