Cycling power-to-weight (W/kg), speed and pace, or swimming pace per 100 m and 100 yd with your SWOLF score.
By AdminDrafted with AI writing toolsUpdated Checked examples: 6
250 W at 75 kg is 3.33 W/kg. 30 km/h is 2:00 per km, so 40 km takes 1:20:00.
For cycling, power-to-weight is power in watts divided by body weight in kilograms (W/kg), and speed converts to pace as 3,600 ÷ km/h seconds per kilometre, with the time for a chosen ride distance. For swimming, pace is time ÷ distance × 100, per 100 m and per 100 yd, and SWOLF adds the average strokes per length to the average seconds per length.
Cyclists compare W/kg as one factor in performance, and swimmers compare SWOLF as a strokes-plus-time score. Cycling speed is entered separately here; it is not predicted from power-to-weight. A 75 kg rider holding 250 W has 3.33 W/kg, and at 30 km/h a 40 km ride takes 1:20:00. A swimmer covering 400 m in 8:00 in a 25 m pool swims 2:00 per 100 m and, at 18 strokes per length, scores a SWOLF of 48.
W/kg ignores aerodynamic drag, which dominates on flat roads. SWOLF scores are comparable only within the same pool length and stroke-counting method.
Power-to-weight is watts divided by body weight in kilograms: a 75 kg rider holding 250 W has 3.33 W/kg. Cycling pace is 3,600 ÷ km/h seconds per kilometer, so 30 km/h is 2:00 per km. Swim pace is time × 100 ÷ meters: 400 m in 8:00 is 2:00 per 100 m.
For watts per pound, divide by weight in pounds instead. The 75 kg rider weighs 165.3 lb, so 250 W is 1.51 W/lb; a 300 W rider weighing 200 lb has 1.50 W/lb, or 3.31 W/kg.
Riders usually quote W/kg at functional threshold power (FTP), the highest power they can hold for about an hour. Allen and Coggan estimate FTP as 95% of the average from a 20-minute test, so a 263 W test gives an FTP of about 250 W.
Compare like with like: a ride average and an FTP give different ratios for the same rider.
W/kg decides climbing speed. On flat roads absolute power and aerodynamic drag matter more, so two riders with the same ratio can ride at different speeds.
Seconds per kilometer = 3,600 ÷ speed in km/h; seconds per mile ≈ 5,793.6 ÷ speed in km/h. At 30 km/h that is 2:00 per km, or 3:13 per mile. Working back, a 2:30 per km pace is 3,600 ÷ 150 = 24 km/h.
Ride time is distance ÷ speed. Forty kilometers at 30 km/h takes 1.333 hours, or 1:20:00, and 25 miles at 20 mph takes 1:15:00. Both assume a steady average speed with no stops.
Pace per 100 m = seconds × 100 ÷ meters. For 400 m in 8:00, that is 480 × 100 ÷ 400 = 120 s, or 2:00.
A yard is exactly 0.9144 m (NIST SP 811), so pace per 100 yd is the per-100 m pace × 0.9144. A 2:00 pace per 100 m becomes 109.7 s, about 1:50 per 100 yd.
To go from yards to meters, divide by 0.9144: 1:30 per 100 yd is 98.4 s, about 1:38 per 100 m. Pool times only compare in the same unit, because 100 yd is 8.6% shorter than 100 m.
SWOLF (swim plus golf) adds strokes per length to seconds per length, and as in golf, lower is better. In a 25 m pool, 400 m is 16 lengths, so 8:00 is 30 s per length; at 18 strokes per length the score is 18 + 30 = 48.
Garmin's own example, 15 strokes in a 30-second length, scores 45. Garmin counts one stroke per full cycle of the arm wearing the watch (Garmin swim terminology), so a count made another way gives a different score for the same swim.
Scores compare only within one pool length. In a 50 m pool every length takes twice as long, so the time part of the same 400 m swim doubles from 30 to 60.
When the distance is not a whole number of lengths, the score uses the average time per length. 410 m in a 25 m pool is 16.4 lengths at 29.3 s each.
Clock times are cut to whole seconds.
| Scenario | Sport | Selected result | Pace |
|---|---|---|---|
| Default | Cycling | 3.33 W/kg | 2:00 per km |
| Swim example | Swimming | 48.0 SWOLF | 2:00 per 100 m |
| Yard pool | Swimming | 37.5 SWOLF | 1:38 per 100 m |
The yard-pool swim is 1:30 per 100 yd, 450 s over 500 yd; its 1:38 per 100 m is the same speed in the longer unit. Its 20 lengths take 22.5 s each, and 15 strokes plus 22.5 s gives 37.5.
The running pace calculator handles run pace and race predictions. For the energy a ride or swim uses, see the calories burned calculator; for training intensity, the heart-rate zone calculator and VO₂ max calculator.
Checked against: 250/75; 250/(75/0.45359237); 3600/30 s/km; 40/30 h
Checked against: 3600 s/h ÷ 150 s/km = 24 km/h
Checked against: 480 s/4 = 120 s per 100 m; × 0.9144 per 100 yd; 18 + 480/16
Checked against: 450 s/5 = 90 s per 100 yd; 450/457.2 m × 100 = 98.4252 s per 100 m; 15 + 450/20
Divide power in watts by body weight in kilograms. A 75 kg rider producing 250 W has 250 ÷ 75 = 3.33 W/kg, or 1.51 W/lb at 165 lb. Riders usually quote W/kg at functional threshold power (FTP), which Allen and Coggan describe as the highest power sustainable for about an hour and estimate as 95 % of the average from a 20-minute test.
SWOLF, from swim and golf, is the number of strokes plus the number of seconds for one pool length, and as in golf a lower score is better. Garmin's example is 15 strokes in 30 seconds, a score of 45. Because it depends on pool length and on how strokes are counted (Garmin counts one per full cycle of the watch arm), scores are comparable only for the same pool and device.
Divide 3,600 by the speed in km/h to get seconds per kilometre: 30 km/h is 120 s, or 2:00 per km, and 24 km/h is 2:30 per km. For pace per mile, divide 5,793.6 by the speed in km/h, because a mile is exactly 1.609344 km: 30 km/h is 3:13 per mile.
Multiply by 0.9144, because 100 yd is exactly 91.44 m. A pace of 2:00 per 100 m (120 s) becomes 109.7 s, about 1:50 per 100 yd. Going the other way, divide by 0.9144, so 1:30 per 100 yd is about 1:38 per 100 m. The yard is defined as 0.9144 m exactly (NIST SP 811).
For information only, not medical advice. These formulas describe populations, not you; talk to a clinician before acting on a result.
This calculator includes 6 worked examples with independently sourced answers. They run in the test suite, and you can run them here too.