What is a good watts per kg?
Divide your FTP by your weight in kilograms — a 245 W FTP at 165 lb (74.8 kg) is 3.27 W/kg — then find yourself honestly in the table below. The bands condense the published Coggan/Allen power-profiling chart, and the print is: they're approximate, riders straddle lines, and the internet's self-reported numbers skew flattering. A season of consistent training typically moves this number by 0.2–0.5; it does not move by whole integers because you bought something.
| Level | Men W/kg at FTP | Women W/kg at FTP |
|---|---|---|
| New to cycling | 0.0–2.0 | 0.0–1.7 |
| Recreational | 2.0–2.8 | 1.7–2.4 |
| Trained | 2.8–3.7 | 2.4–3.2 |
| Competitive amateur | 3.7–4.7 | 3.2–4.0 |
| Elite amateur | 4.7–5.6 | 4.0–4.8 |
| World class | 5.6+ | 4.8+ |
Condensed from the published Coggan/Allen power-profiling table (FTP duration). Bands are guides, not gates — the calculator above places you in both columns.
The denominator moves more day to day than the numerator: hydration alone swings a rider a kilogram or two, which is ±0.1 W/kg of pure noise. Weigh in the same way every time — morning, after the bathroom, before breakfast — and judge trends over weeks. Chasing a daily W/kg number is how good training turns into bad eating.
Why W/kg rules the climbs — and raw watts rule the flats
Going uphill, nearly all your power fights gravity, and gravity charges by the kilogram — so the climb sorts riders almost purely by W/kg. On the flat, the enemy is air, which doesn't care what you weigh: raw watts (and aerodynamics) decide. That's why a 90 kg rider holding 300 W (3.33 W/kg) drops a 65 kg rider holding 250 W (3.85 W/kg) on the flat — and gets dropped on the first real climb. Neither number is "better"; they answer different terrain. The power ↔ speed calculator prices the flat half of that trade and the climb time calculator the uphill half, at your numbers.
How does W/kg translate to climb time?
Directly, and the physics engine can print it. A 165 lb rider on a 19 lb bike, holding steady power, up two well-known climbs:
| W/kg | Old La Honda (5.4 km at 7.3%) | Alpe d'Huez (13.8 km at 8.1%) |
|---|---|---|
| 2.5 | 31:54 | 1:29:22 |
| 3.0 | 26:51 | 1:15:02 |
| 3.5 | 23:16 | 1:04:53 |
| 4.0 | 20:37 | 57:19 |
| 4.5 | 18:34 | 51:28 |
| 5.0 | 16:56 | 46:50 |
Martin power model: paved road, hoods, still air, published length and average grade. W/kg here is watts ÷ rider weight; the engine hauls rider plus bike.
Read the Alpe column downward: going from 3 to 4 W/kg saves about 18 minutes, but 4 to 5 saves only about 10 — the minutes get cheaper as you climb the table, because at higher speeds a growing share of each extra watt goes into the air rather than into altitude. The climb time calculator runs any climb at your own weight and power, and the VAM calculator turns a climb you've already ridden back into the W/kg it took.
What W/kg do you need to race?
Road racing categories in the US are earned with results, not watts, so there is no official number — the figures forums quote (roughly 3 W/kg at threshold to hang in a Cat 4/5 field, 3.5–4 for Cat 3, 4 and up for Cat 1/2) are folk estimates drawn from the same power-profiling chart as the table above, and should be read that way. The one place W/kg has actually been a gate is virtual racing:
| Zwift pace group | W/kg, 20-minute power |
|---|---|
| A | 4.0 and up |
| B | 3.2–3.9 |
| C | 2.5–3.1 |
| D | under 2.5 |
The traditional Zwift bands. Zwift now assigns race categories from a results-based rating rather than raw W/kg, but the bands survive as pace-group labels and as the shorthand everyone uses.
Two cautions. A category number is the floor for the bunch, not a portrait of the winner — races are decided by one- and five-minute power, positioning and luck, none of which threshold W/kg captures. And a strong W/kg in a light rider still loses the flat sprint to raw watts, which is the previous section again.
Does the duration matter — 5-minute vs 20-minute vs FTP W/kg?
Yes, and mixing them is the most common way the internet inflates its numbers. The Coggan/Allen profile has separate columns for 5 seconds, 1 minute, 5 minutes and FTP; the bands above are the FTP column. The same world-class rider posts something like 24 W/kg for five seconds, 11 for a minute and 7.5 for five minutes — every duration has its own scale, and a five-minute number read against the FTP table flatters you by a whole category. The calculator divides whatever you enter; just compare like with like, and when you read the table use the number the FTP calculator gave you, not your best five minutes.
Estimated sustained outputs for the best Grand Tour climbers on summit finishes run around 5.8–6.3 W/kg for 30–40 minutes — estimates, because teams rarely publish power files. Useful perspective: the gap between "trained" and "world class" is about the same size as the gap between "new to cycling" and "trained." The second half of the table is mostly picking your parents.
How to improve your watts per kg
The fraction has two ends, and the right end depends on where you are. Newer and returning riders should almost always work the numerator: structured time in Zone 2 and threshold reliably adds 10–20% to FTP in a couple of seasons, while aggressive weight loss on a training load mostly subtracts from the power side too. Already trained and carrying genuinely spare weight? Modest, slow loss — a few hundred grams a week, fueled workouts — converts cleanly. The classic mistake is running both projects at full throttle at once; that's how W/kg goes down.
How much does losing weight change W/kg — and your climb time?
The same 245 W FTP, at four body weights, priced on Alpe d'Huez by the physics engine:
| Rider weight | W/kg at 245 W | Alpe d'Huez time |
|---|---|---|
| 165 lb | 3.27 | 1:09:05 |
| 160 lb | 3.38 | 1:07:22 |
| 155 lb | 3.48 | 1:05:40 |
| 150 lb | 3.6 | 1:03:58 |
19 lb bike, paved road, hoods, still air. Assumes the watts survive the weight loss — which is the assumption that usually fails.
Fifteen pounds at the same 245 W is worth 5:07 on the Alpe. Adding 10% to FTP at the same weight (245 → 270 W) is worth 6:01. Roughly the same prize from either end of the fraction — which is the point of the section above: pick the end you can actually move without wrecking the other.
Does bike weight count?
Not in this number — the convention everywhere (racing categories, Zwift, the table above) is rider weight only. Gravity, however, hauls the whole system: rider, bike, bottles, tools. Your Garage tracks system weight per bike and the climb time calculator uses exactly that — which is also why a four-figure kilogram of carbon buys seconds, and a free kilogram of rider buys the same seconds (the wheel weight calculator prices any grams, anywhere on the bike, on any of these climbs).