Pace Calculator — Running, Swimming & Race Planner
Calculate running pace, swim splits with CSS and pool conversions, or plan ultra race cutoffs with aid station timing. Supports Running, Swimming, and Race Planner modes.
Last updated: 2026-03-27
Pace calculator
Enter your values
Calculate running pace, swim splits and CSS, or plan ultra race cutoffs. Choose your sport above.
Result
--
Enter a completed distance and time to calculate pace, or set up a race plan with cutoff and aid stations.
Calculation History(0)
Example calculations
Tap an example to prefill the calculator with sample values.
Steady 5K
5 km in 26:15
A common benchmark where average pace and 10K prediction are still easy to interpret.
Result: Average pace about 8:27 per mile and a 10K projection near 54:44
Half marathon pace check
13.1 miles in 1:52:00
Shows how the calculator keeps working when the effort is already near a long-race target.
Result: Average pace about 8:33 per mile with marathon projection just under four hours
1500m swim — SCM pool
1500m in 22:30 (25m pool)
A common distance trial for competitive and fitness swimmers. Shows pace per 100 and pool conversions.
Result: Pace 1:30/100m with CSS ~1:27/100m and pool conversion estimates
100-mile ultra — 30hr cutoff
100 miles, 30-hour cutoff, 15 aid stations
Classic ultra scenario — shows required moving pace after deducting aid station time.
Result: Required moving pace ~16:33/mi after 2 hours of total aid time
How the pace estimate works
Average pace is simply time divided by distance, but it becomes more useful when you can see that pace in both miles and kilometers, compare it to hourly speed, and map it onto common race targets.
The race projections here use a standard endurance-scaling formula. That makes them good planning anchors, but not guarantees, especially when you are projecting far beyond the distance you actually raced or trained.
Swimming mode uses the same time-over-distance approach but reports pace per 100m/yd and converts between pool formats using standard FINA approximation factors. CSS (Critical Swim Speed) is derived from your 200m and 400m times — it represents your sustainable threshold pace.
Race Planner mode deducts total aid station time from the cutoff to calculate required moving pace. Station-by-station targets show where your buffer is thin so you can plan your effort distribution.
Pace calculator FAQs
How to interpret pace, speed, swim splits, and race cutoff planning.
What is the difference between pace and speed?
Pace tells you how long it takes to cover one mile or one kilometer, while speed tells you how many miles or kilometers you would cover in an hour. Runners usually train by pace because it is easier to compare directly against race goals and splits.
Why show both mile and kilometer pace?
Different runners and race formats use different standards. Showing both makes it easier to compare workouts, race goals, and treadmill or GPS readouts without doing mental conversion.
How do the race projections work?
The projections use a standard Riegel-style endurance formula. It scales your current effort to longer or shorter races, which is useful for planning, but it still assumes similar fitness, endurance durability, and race execution.
Why are long-distance projections less reliable from short efforts?
A fast short effort can make marathon potential look better than your current endurance really supports. The farther the target race is from the effort you entered, the more the projection depends on assumptions about aerobic durability and fueling.
What is CSS (Critical Swim Speed)?
Critical Swim Speed is your estimated threshold pace in the pool, calculated from your 200m and 400m times using the formula CSS = (400 - 200) / (T400 - T200). Swimming at or near CSS trains your aerobic endurance. It's the swim equivalent of lactate threshold pace in running.
How do pool conversion factors work (SCY, SCM, LCM)?
Pool conversions use standard approximation factors: SCY to SCM ×1.11, SCM to LCM ×1.02. These account for the turn frequency difference between pool sizes. They're accepted estimates for planning purposes, but individual variation (especially turn and pushoff technique) can shift actual times.
How does the Race Planner calculate required pace?
The Race Planner subtracts total aid station time (stations × minutes per stop) from the cutoff time to get your available moving time, then divides by race distance. It shows target arrival times and buffer minutes at each station, flagging any with less than 15 minutes of buffer as risk zones.
Embed this calculator
Copy the code below to embed this calculator on your website or blog. It's free — no API key needed.
<iframe src="https://calc.mintloop.dev/embed/hobby/pace-calculator" width="100%" height="600" frameborder="0" title="Pace Calculator — Running, Swimming & Race Planner" loading="lazy"> </iframe>
Optional: auto-resize script
<script>
var CALC_HUB_ORIGIN = 'https://calc.mintloop.dev';
window.addEventListener('message', function(e) {
if (e.origin !== CALC_HUB_ORIGIN) return;
if (!e.data || e.data.type !== 'calc-hub-resize') return;
var frames = document.querySelectorAll('iframe[src*="calc.mintloop.dev"]');
frames.forEach(function(f) {
if (f.contentWindow === e.source) {
f.style.height = String(Math.max(0, Number(e.data.height) || 0)) + 'px';
}
});
});
</script> Related tools
Pair pace estimates with nearby endurance, hydration, and recovery tools.
Get more training calculators
Join the Calc Hub newsletter for new calculators covering running, endurance, recovery, and race prep.
Join the Calc Hub newsletterWas this calculator helpful?
Your feedback helps us improve future calculators.