Open Water Swim Calculator: Pool to Open Water Pace Converter
Convert your pool swim pace to open water time. Open water is typically 10 to 20% slower than pool. Enter your pool pace and race distance to get a predicted open water finish time with wetsuit, current, and sighting adjustments. Built for triathlon swim planning and open water race prediction.
Quick Answer
How much slower is open water swimming vs pool? Open water swimming is typically 10 to 20% slower than pool swimming at the same effort. A swimmer with a 1:40/100m pool pace, which is 1:31/100yd, will swim approximately 1:50 to 2:00/100m, or 1:41 to 1:50/100yd, in open water. The difference comes from: no wall push-offs (+5%), sighting and navigation (+3 to 5%), waves and chop (+2 to 5%), and no lane lines (+2%). Wetsuits partially offset this by improving buoyancy (-3 to 5%).
:min : sec /100m
World Aquatics allows 3 to 5 mm of material and makes a wetsuit compulsory below 18 degrees, optional from 18 to 20.
How often you lift your head to navigate
Open Water Estimate
30:30
estimated finish time
2:02open water pace /100m
Comparable to pool pace
Factor
Adjustment
Pool pace (baseline)
2:00 /100m
Wetsuit
-12s/100m
Sighting
+6s/100m
Conditions
+8s/100m
Current
0s/100m
Open water pace
2:02 /100m
Total adjustment
+2s/100m slower
Estimates based on typical amateur swimmer adjustments. Actual times vary with water temperature, course accuracy, drafting, and individual experience.
This calculator is for reference only. Open water conditions vary significantly. Always check water temperature, currents, and weather before swimming in open water.
One thing on this page is a governing body's and the rest is not. The wetsuit rule is World Aquatics, with the water temperature and the 3 to 5 mm thickness written into its open water regulations, and the triathlon organisers set their own limits on top of it. The seconds are ours. Nobody publishes a table of what sighting, chop or a current costs per hundred metres, so the adjustments this calculator adds, and the three condition levels in the chart below, are this site's own convention, chosen to sit inside the ten to twenty per cent that open water swimming is generally slower. Your own first open water swim against the clock beats every one of them.
Pool to Open Water Pace: Conversion Chart
Pool to Open Water Pace: Conversion Chart
Predicted open water pace per 100m for a given pool pace, across three condition levels (wetsuit assumed). The chart stays in metres; to read a row per 100 yd, multiply the time by 0.9144, so a 2:00 becomes 1:50. The calculator above does that for you when the page is set to imperial.
Pool Pace (/100m)
Calm Open Water
Moderate Chop
Rough Conditions
1:20
1:28 to 1:32
1:32 to 1:38
1:38 to 1:46
1:30
1:39 to 1:44
1:44 to 1:50
1:50 to 1:59
1:40
1:50 to 1:56
1:56 to 2:02
2:02 to 2:12
1:50
2:01 to 2:08
2:08 to 2:14
2:14 to 2:25
2:00
2:12 to 2:20
2:20 to 2:26
2:26 to 2:38
2:10
2:23 to 2:32
2:32 to 2:38
2:38 to 2:51
2:20
2:34 to 2:44
2:44 to 2:52
2:52 to 3:04
Calm = lake, no wind. Moderate = light waves, some current. Rough = ocean swell, strong current, or choppy conditions. Wetsuit assumed for all values. Without wetsuit, add 3 to 5% to all times.
Open Water Race Time Estimates
Predicted open water race times by pool pace for the four standard triathlon distances. The pool pace column is per 100 m; per 100 yd it reads 1:13, 1:22, 1:31, 1:41, 1:50, 1:59 and 2:08. The finish times are unaffected, because the distance swum is the same.
Pool Pace (/100m)
750m (Sprint)
1500m (Olympic)
1900m (70.3)
3800m (Ironman)
1:30
13:00
27:00
34:00
70:00
1:40
14:30
30:00
38:00
78:00
1:50
16:00
33:00
42:00
86:00
2:00
17:30
36:00
46:00
94:00
2:10
19:00
39:00
50:00
102:00
2:20
20:30
42:00
54:00
110:00
Times include ~10% open water adjustment for moderate conditions with wetsuit. Sprint/Olympic distances per World Triathlon standards, 70.3 and Ironman per WTC standards.
Why Open Water Is Slower Than Pool
Five factors make open water swimming slower: (1) No wall push-offs: in a pool, you push off every 25m or 50m, gaining 2 to 3 seconds each time. Over 1500m in a 25m pool, that's 60 push-offs saved in open water. (2) Sighting: lifting your head to navigate adds drag and breaks your stroke rhythm, costing 3 to 5% efficiency. (3) Waves and chop: even light waves disrupt breathing timing. (4) No lane lines: without lane ropes to dampen turbulence, you fight more water movement. (5) Currents: even mild currents add time on at least one leg. Calculate your pool baseline pace with our swim pace calculator, which you will need as input for open water prediction.
Wetsuit Advantage: How Much Faster?
A swimming wetsuit improves speed by 3 to 5% through better buoyancy and body position. The legs float higher, reducing drag. A 2:00/100m pool swimmer, which is 1:50/100yd, might swim 1:55 to 1:58/100m in a wetsuit in calm water, or 1:45 to 1:48/100yd. Most triathlon races allow wetsuits when water temperature is below 24.5°C (76°F) for World Triathlon and the same 24.5°C for Ironman. Non-wetsuit open water swimming is 3 to 5% slower than wetsuit. Track your swimming efficiency with our SWOLF calculator. Combine your swim time with bike and run for a full race prediction: triathlon finish time calculator.
Why open water pace is different
Swimming in open water involves five additional challenges that pool training does not replicate, each adding seconds to your pace at the same effort.
The five factors
Sighting: Lifting your head every 10 to 15 strokes to navigate adds 3 to 10 seconds per 100m and disrupts body position. Practice in open water to minimise this.
No push-offs: Wall turns contribute 3 to 5% to pool speed. In open water, you swim every metre, adding roughly 5 seconds per 100m equivalent.
Water conditions: Chop, waves, and wind add 5 to 25 seconds per 100m. Calm lakes are close to pool conditions; sea swims can be significantly slower.
Navigation drift: Even experienced swimmers swim 3 to 8% extra distance due to course deviation. Sighting reduces this but never eliminates it.
Wetsuit buoyancy: A well-fitted wetsuit raises your body position, reducing drag significantly. A standard suit saves 10 to 15 seconds per 100m, often offsetting all other open water penalties.
With a wetsuit in calm conditions, most swimmers go faster in open water than in the pool. The buoyancy advantage outweighs all other factors.
Wetsuit rules and performance
Wetsuit legality in triathlon is governed by water temperature. World Triathlon (ITU) enforces strict rules, and IRONMAN events follow similar guidelines.
Temperature rules (World Triathlon)
Below 16°C (61°F): Wetsuit required for safety
16°C to 22°C (61°F to 72°F): Wetsuit optional. Athletes with one gain a speed advantage.
Above 22°C (72°F): Wetsuits prohibited (illegal to wear).
Wetsuit types
Full suit: Full arm and leg coverage, maximum buoyancy and warmth. Best for cold water.
Sleeveless: Legs covered, arms free. Reduced shoulder restriction for strong swimmers. Less buoyancy gain.
Racing suit: Thinner neoprene on arms, strategic panelling. Marginally faster in warm optional-wetsuit conditions.
Sizing matters
A poorly fitted wetsuit restricts breathing and shoulder rotation, adding significant fatigue. Always try before you race. A suit that compresses your chest when in swim position is too small.
World Aquatics, the body called FINA until 2022, sets both bounds: material at least 3 mm and at most 5 mm thick. A wetsuit is compulsory below 18 degrees and optional between 18 and 20. It must cover torso, back, shoulders and knees, and must not extend past the neck, wrists or ankles. Triathlon wetsuits are typically 3 to 5mm, which is inside that band. World Aquatics, Competition Regulations, in force from 25 June 2025.
Race day tactics for open water
Open water race performance depends as much on strategy as fitness. These tactics can save 2 to 5 minutes without any improvement in swimming fitness.
Starting position
Seed yourself based on realistic pace. Starting too far forward means congestion and contact. Too far back means extra navigation around slower swimmers. Find the edge of your seeded group for cleaner water.
Drafting
Swimming directly behind another swimmer's feet reduces your energy cost by 15 to 20%. This is legal in all triathlon and open water events. Find a swimmer slightly faster than you and hold their feet for as long as possible.
Sighting technique
Use a brief "alligator eye": lift only your eyes above the water surface during the recovery phase, rather than a full head lift. Sight every 10 to 15 strokes and pick a landmark above the buoy (a building, tree) for consistency.
T1 wetsuit removal
Unzip your wetsuit in the last 50m of the swim. Exit the water, pull to your waist while running, then step out (not step, step, step; one smooth motion per foot). Practice this before race day.
Drafting is legal in all World Triathlon, IRONMAN, and open water events. The only prohibited action is physically impeding another swimmer.
Frequently asked questions
How much slower is open water than pool?
Open water swimming is typically 10 to 20% slower than pool swimming at the same effort level. In calm conditions with a wetsuit, expect 10 to 12% slower. In rough conditions without wetsuit, expect 15 to 20% slower. The main factors are no wall push-offs, sighting, and waves.
How do I predict my triathlon swim time?
Take your pool pace per 100m, add 10 to 15% for open water conditions, then multiply by the race distance. Example: 1:40/100m pool pace (1:31/100yd) → ~1:50/100m open water (1:41/100yd) → 1500m Olympic swim ≈ 27:30. Use the calculator above for a more precise estimate.
Does a wetsuit make you faster in open water?
Yes, wetsuits improve speed by approximately 3 to 5% through better buoyancy and reduced drag. The legs sit higher in the water, creating a more streamlined body position. Most triathlon races permit wetsuits below 24.5°C (76°F) water temperature.
How do I sight properly in open water?
Lift your eyes (not your whole head) every 6 to 8 strokes to spot a landmark. Integrate sighting into your breathing stroke: as you breathe, lift your eyes slightly forward before turning to breathe. Practice in the pool by swimming head-up freestyle for 25m sets.
How much slower is open water swimming than pool swimming?
Without a wetsuit, open water swimming is typically 5 to 15% slower than pool pace at the same effort. The main reasons are sighting (lifting your head to navigate costs 3 to 10 seconds per 100m), absence of wall push-offs, water conditions, and navigational inefficiency. With a well-fitted wetsuit, the buoyancy advantage can offset most of these factors, making wetsuit open water pace comparable to or faster than pool pace for many swimmers.
How much faster does a wetsuit make you in open water?
A standard triathlon wetsuit typically improves open water pace by 8 to 15 seconds per 100m compared to swimming without one. The improvement comes from increased buoyancy (higher body position reduces drag), warmth (allowing better muscle function), and the psychological confidence of feeling more supported in the water. Racing wetsuits with thinner arms offer slightly more improvement due to reduced shoulder restriction.
What is sighting in open water swimming?
Sighting is the technique of lifting your head during freestyle to look forward and navigate toward a buoy or landmark. It is necessary in open water where you cannot follow a lane line. Each sighting action causes a slight body position drop that costs 3 to 8 seconds per 100m depending on how often you sight and your technique. Experienced swimmers minimise this by sighting every 15 to 20 strokes using a brief forward glance rather than a full head lift.
How do I calculate my open water swim time for a triathlon?
Start with your pool pace per 100m, or per 100yd if that is how you train, and keep every figure on the same base. Add adjustments for sighting (+3 to 10 sec/100m), water conditions (+0 to 25 sec/100m), and subtract the wetsuit advantage if wearing one (-8 to 15 sec/100m). Multiply your adjusted pace by the distance in 100m units. For example: 2:00/100m pool pace + 6s sighting + 8s chop - 12s wetsuit = 2:02/100m open water pace × 19 (for 1900m) = 38:38. Per 100 yd that is 1:50 becoming 1:52; the arithmetic is the same and the finish time does not change.
Does current affect open water swim time significantly?
Yes. A moderate favourable current (river, tidal) can reduce swim time by 10 to 25 seconds per 100m, saving several minutes on a triathlon swim. Swimming against current adds the same penalty. Most triathlon courses are designed as loops to neutralise current effects, but point-to-point open water races can be significantly affected. Check race conditions and course map before estimating your time.
What water temperature requires a wetsuit?
World Triathlon (ITU) rules require wetsuits when water temperature is below 16°C (61°F) and prohibit them above 22°C (72°F). Between 16°C and 22°C (61°F and 72°F), wetsuits are optional. Ironman events follow similar rules with slight variations. Below 16°C (61°F), a wetsuit is strongly recommended for safety regardless of rules. Water temperature also affects performance; cold water (below 18°C, or 64°F) can cause significant muscle efficiency reduction.
How can I improve my open water swimming?
The biggest improvements come from practising sighting technique (reduces the pace penalty significantly), swimming in open water regularly before racing (reduces navigation anxiety and improves confidence), drafting behind other swimmers (reduces energy cost by 15 to 20%), and starting in a position that matches your pace to avoid early congestion. Pool fitness is necessary but not sufficient. Open water specific skills are learned only in open water.
Is a 1500m open water swim hard?
A 1500m open water swim is the Olympic triathlon distance. For a swimmer with consistent pool training (3 to 4 sessions per week), it is comfortably achievable. With a wetsuit in calm conditions, most recreational swimmers who can complete 1500m continuously in a pool will finish the open water distance in 25 to 40 minutes. Without a wetsuit in choppy conditions, expect 5 to 10 minutes longer than your pool time.