Swim Pace Converter
m:ss
Same speed, per 100 yards
1:22
4,000 metres per hour
- One 25 m length0:23
- 50 m0:45
- 200 m3:00
- 1500 m22:30
Interval set
How this was worked out
- Pace in seconds1:30 per 100 metres = 90 s
- The course ratio100 yards is 91.44 m against 100 m, so 90 × 0.9144 = 82.3 s = 1:22
- One repeat of the set90 s per 100 m × 100 ÷ 100 = 90 s = 1:30
- Send-off, rounded up90 + 20 = 110 s, up to the next 5 s = 1:50, leaving 20 s rest
- The set, end to end110 × 9 + 90 = 1,080 s = 18:00
The conversion is a distance ratio and nothing more: a yard is exactly 0.9144 m, so 100 yards is 91.44% of 100 metres and a pace for it is 91.44% of the time. It assumes the same speed through the water, which is why a short-course time does not transfer — more walls means more push-offs, and what those are worth is personal. The rules of thumb in circulation for that adjustment have no published derivation behind them, so this page does not ship one.
The set clock stops when the last repeat touches, not at the top of the next send-off, so the total above is pool time rather than lane time. Send-offs round up: rounding one down would quietly take back rest you asked for, and the rest figure shown is what the rounding actually leaves rather than what was typed.
Two pools, two units, one swimmer
Swimming is the sport where the unit changes with the building. A pool in most of the world is 25 or 50 metres; a great many pools in the United States are 25 yards, and the sets written on the whiteboard beside them are in yards too. A swimmer who trains in one and races in the other needs a way to read a target pace in whichever unit is painted on the wall.
That is the first half of this page: enter a pace per 100 in the unit you have, read it back in the other. The second half turns that pace into a set — repeats, distance, rest — and gives the send-off to call it on.
A yard is 0.9144 metres, and that is the whole conversion
One hundred yards is 91.44 per cent of one hundred metres, so a pace for it is 91.44 per cent of the time. A 1:30 hundred metres is a 1:22.3 hundred yards. Nothing else is added, and the omission is deliberate: adjustments of the "add five seconds" kind circulate widely but come with no derivation and no published source behind them, and this site does not print numbers it cannot attribute.
The honest caveat is that a converted time is not a predicted time. A shorter pool means more walls, and a wall is a push-off — free speed for a swimmer with a strong underwater phase and an interruption for one without. How much your own turns are worth is measurable with a stopwatch in an afternoon, and it is personal enough that nobody should hand you an average for it.
Send-offs land on round numbers for a reason
Sets are called off a pace clock with a sweeping hand, and a swimmer glancing up mid-set can read the top, the quarter and the half far more reliably than an arbitrary figure. That is why intervals come out as 1:45 and 2:00 rather than 1:47. Enter the rest you want and the send-off is rounded up to whichever granularity you call on — five, ten or fifteen seconds.
It always rounds up. Rounding a send-off down would hand back less recovery than was asked for, and on a long set that is the difference between an aerobic session and an accidental threshold one.
Reading the set the tool builds
Ten by one hundred metres at 1:30 with twenty seconds rest comes back as a 1:50 send-off and a total of eighteen minutes for a kilometre of swimming. Notice that the total is not eleven times the send-off: the clock stops when the last hand touches the wall, because the rest after the final repeat belongs to whatever comes next in the session.
That distinction is worth a few minutes over a full session, and it is why a written workout so often outlasts the lane time booked for it. If you are planning around a shared lane or a pool that closes, add your own rest between sets rather than trusting the arithmetic to have hidden it somewhere.
Yards against metres, send-offs and rounding
Is my short-course yards time equivalent to a long-course metres time?
No, and the gap is real rather than a rounding error. A 25-yard pool gives you four turns per hundred against one in a 50-metre pool, so the converted figure here tells you what the same swimming speed would produce, not what you would actually touch the wall in.
Why is 100 yards not simply ninety per cent of 100 metres?
Because the international yard is defined as exactly 0.9144 metres, which makes the ratio 91.44 per cent. At a 1:40 hundred metres that difference between 90 and 91.44 per cent is about a second and a half — small, but it compounds across a long set.
How much rest should I put in?
That depends entirely on what the set is for, and this page has no opinion about it. It takes the rest you specify, adds it to the swim time and rounds the total up to a callable interval, leaving the coaching decision where it belongs.
Can I use a pace measured in metres for a set in a yards pool?
Yes, and it is one of the reasons the two halves of the page are separate. Enter your pace in whichever unit you know it in, set the pool to the unit the set is written in, and the pace is moved across before the repeats are calculated.
What does the "no rounding" option do?
It reports the send-off as the exact sum of the repeat time and the rest you asked for, to the second. It is useful when a watch or a tempo trainer is doing the counting rather than a wall clock and a coach.