Swimming Distance & Lap Counter

Swimming Distance Guide

What's the key thing to understand about Pool Lengths and Distance?

25m pool: 2 lengths = 50m. 4 lengths = 100m. 20 lengths = 500m. 40 lengths = 1000m (1km). 60 lengths = 1500m (approximately a mile — 1 mile = 1609m = 64.4 lengths). 50m pool: 2 lengths = 100m. 20 lengths = 1000m. 30 lengths = 1500m. 76 lengths = 3800m (Ironman). A lap vs a length: in swimming, confusion exists. In most UK leisure pools, 'one lap' = one length (one way). In American usage, 'one lap' often means two lengths (there and back). This calculator uses lengths, meaning one way, but always confirm which convention a pool or event is using before comparing distances or times between sources.

What do I need to know about Calorie Burn in Swimming?

Swimming burns significantly fewer calories than running at the same time because: water support reduces effort against gravity. Less post-exercise oxygen consumption. Cooling effect of water reduces thermogenic calorie burn. Approximate calorie burn (75kg swimmer): easy freestyle: 400-500 kcal/hour. Moderate freestyle: 500-600 kcal/hour. Fast/competitive: 600-700 kcal/hour. Breaststroke: 500-650 kcal/hour (higher energy per metre). Butterfly: 600-800 kcal/hour (most demanding). For weight loss purposes, swimming's low-impact nature means many people can sustain longer sessions than with higher-impact cardio, which can offset its slightly lower calorie burn per minute compared to running.

What's the difference between Open Water and Pool Swimming?

Converting pool pace to open water time: most swimmers are 3-8% slower in open water. Factors slowing open water times: sighting (lifting head to navigate — 3-5% energy cost). No walls to push off. Chop, current, and navigation error. Wetsuit: adds buoyancy — can improve speed 3-5% vs pool. Net effect: for the same fitness level, open water times are usually slightly slower than pool times, but wetsuit-legal races may be comparable or faster. Distances: triathlon swim courses are measured along the actual swim route, which is rarely a perfectly straight line, so the true distance covered is often somewhat longer than the official course distance suggests.

What do I need to know about Building a Swim Training Plan?

Total weekly yardage approach: beginners: 1000-2000m/week in 2-3 sessions. Intermediate: 3000-5000m/week. Advanced: 5000-10,000m/week. Session structure: warm-up (400-600m easy). Main set (intervals or continuous). Cool-down (200-400m easy). Interval examples: 10×100m with 20 seconds rest (builds pace and efficiency). 5×200m descending (getting faster each set). 1×1500m continuous (builds aerobic base). The drill set — kick on side, catch-up, fingertip drag, single-arm — targets specific technique elements individually, isolating one aspect of the stroke at a time for focused improvement.