Health⏱ 4 min read
How to Calculate Swimming Distance and Track Your Yardage
Pool lengths, metres, yards, and open-water distances create confusion. Here's how to convert between them accurately and how to track cumulative distance for training goals.
Swimming distance tracking gets complicated by the variety of pool lengths, the mix of metres and yards in different countries, and the challenge of tracking open-water swims. Here's a complete guide to getting the numbers right.
Standard Pool Lengths
Pool TypeLengthCommon Use
Short course metres (SCM)25mMost UK leisure pools and clubs
Long course metres (LCM)50mOlympic / competition pools
Short course yards (SCY)25 yards (22.86m)Common in USA
Key Conversion Factors
1 mile = 1,609.34m = 1,760 yards = 64.37 lengths (25m pool)
1 km = 1,000m = 40 lengths (25m pool) = 20 lengths (50m pool)
1,500m (Olympic triathlon) = 60 lengths (25m pool)
3.8km (Ironman) = 152 lengths (25m pool)
Metres to yards: x 1.0936
Yards to metres: x 0.9144
SCY to SCM pace conversion (same effort):
SCM pace (per 100m) = SCY pace (per 100y) x 1.11
(25m pools are slower than 50m due to more turns)
Lengths to Distance
Distance = Lengths x Pool length
25m pool, 40 lengths: 40 x 25 = 1,000m = 1km
25m pool, 64 lengths: 64 x 25 = 1,600m ≈ 1 mile
50m pool, 30 lengths: 30 x 50 = 1,500m (Olympic distance)
Common training session distances:
400m = 16 lengths (25m) or 8 lengths (50m)
1,000m = 40 lengths (25m) or 20 lengths (50m)
1,500m = 60 lengths (25m) or 30 lengths (50m)
2,000m = 80 lengths (25m) or 40 lengths (50m)
Tracking Open-Water Swims
GPS watches with open-water swim mode are the most practical method. Points to know:
- GPS underwater is blocked — watches sample position at the surface only, recording between arm strokes
- Expect 3-8% distance error from GPS in open water — more in choppy conditions
- Straight-line swims in a buoy-marked course are most accurate
- Tidal or current-affected water means your GPS distance isn't the same as your effort distance
Approximate open-water to pool equivalence:
Open-water swimming typically feels harder than pool swimming
due to navigation, wetsuit restriction, drafting, and current.
Rule of thumb for training load comparison:
1km open water ≈ 1km pool (same aerobic load, despite feeling harder)
Pace is not directly comparable due to drafting and GPS error.
Annual Distance Goals
Common annual mileage targets for adult swimmers:
Recreational (2-3 sessions/week): 100-200km/year
Club swimmer: 300-600km/year
Competitive masters: 600-1,000km/year
Elite: 2,000-3,000km+/year
If swimming 3 sessions/week, 1,500m each:
= 4,500m/week = 234km/year (good recreational target)