How this works
Swim pace is universally expressed as "time per 100", either per 100 metres (long-course or short-course pools, most international competitions) or per 100 yards (most US pools). Calculating it is just a unit conversion: pace_per_100 = (total_time / total_distance) × 100. A 1500-metre pool swim in 30:00 is a pace of 2:00 per 100 metres, average speed 3.0 km/h.
Reference points for context. Olympic 1500-metre freestyle finals run around 1:00 per 100m (sub-15-minute total). Competitive masters swimmers in their 30s-40s typically train at 1:30–1:45 per 100m. Recreational fit swimmers often hold 2:00–2:15 per 100m for a 1500m. Beginners breaking into long-form swimming often start at 2:30+ per 100m and improve rapidly with technique drills before any conditioning gains.
A few practical notes. (1) Pool swims and open-water swims are not directly comparable. Open water typically adds 5–15% per 100 because of wetsuit drag, sighting, current, and waves. (2) Pace varies a lot with stroke: freestyle is fastest, butterfly second (in short bursts only), backstroke next, breaststroke slowest. The "pace per 100" benchmark assumes freestyle unless you note otherwise. (3) Triathletes typically swim somewhat slower than dedicated pool swimmers because they train across three sports — a 1:30/100m at the pool might become 1:45–2:00/100m in race-specific open water effort.
The formula
distance is the total distance swum. time is the total swim time. The "100 unit" is whichever you swam in (metres or yards). Standard practice: pool swims report in the units of the pool (100m for international, 100yd for most US clubs); the unit travels with the result.
Example calculation
- Swam 1500 m in 30:00 (1800 seconds).
- Pace = (1800 / 1500) × 100 = 120 sec = 2:00 per 100m. Speed = 1500 / 1800 = 0.833 m/s = 3.0 km/h.
Frequently asked questions
How does pool pace differ from open-water pace?
Open water is almost always 5–15% slower per 100 than your pool pace, sometimes more. Why: wetsuit drag (typical), needing to lift your head to sight, current and chop, no walls to push off (a free-pool swimmer gains a small but real boost from each turn), and the psychological effects of dark, deep water. For triathlon goal pacing, take your pool 1500m time and add 10–20 seconds per 100m — that's a realistic open-water target. Practice in open water before race day if at all possible; the technique adjustments matter more than the conditioning.