Pace Calculator

Pace, time, and distance are three sides of the same relationship — know any two, and the third follows automatically. This calculator works in whichever direction is useful: find your pace from a distance and time, find a finish time from a distance and target pace, or find how far you went from a time and pace. It converts between miles and kilometers automatically and projects your current pace across common race distances.

How the calculations work

Everything else this calculator shows — speed in mph or km/h, per-km pace if you entered per-mile (or vice versa), and projected times for other race distances — is derived from whichever one of these three you’re solving for. Speed and pace are simply inverses of each other expressed in different units: pace is time per unit distance (minutes per mile), while speed is distance per unit time (miles per hour), so converting between them is just a matter of flipping the fraction and adjusting units (60 minutes per hour, divided by pace in minutes, gives speed in mph).

This calculator offers three modes specifically because different situations naturally start from different known pieces of information. After a race or training run, you typically know the distance and your finish time and want to know your pace — that’s “Find Pace” mode. When planning ahead for a goal race, you typically know the distance and want to work out what pace hits a specific target time — that’s “Find Finish Time,” used in reverse by fixing pace and reading off the time, or more commonly used directly to check what a candidate pace would produce. When you’ve run for a set amount of time without tracking distance precisely (a treadmill session, or a run where GPS lost signal), “Find Distance” reconstructs an estimated distance from time and a known or assumed pace.

Any GPS-based distance measurement carries some inherent imprecision — satellite signal quality, tree cover, tall buildings, and tunnels can all cause a GPS watch to slightly over- or under-report actual distance covered, typically by a small percentage rather than a large one. This is worth keeping in mind specifically when using “Find Pace” mode with a GPS-measured distance: the resulting pace inherits whatever small measurement error came from the distance figure, which is part of why official race splits (measured against a certified, fixed course) sometimes disagree slightly with a runner’s own GPS watch reading for the same race.

Worked example

Using this calculator’s own default example — a half marathon (13.1 miles) finished in 1:45:00:

From that same 8:01/mile pace, the calculator projects finish times for other common distances: a 5K would finish around 24:56, a 10K around 49:52, and a full marathon around 3:30:20 — all assuming the exact same pace is held for the entire distance, which is itself a simplification worth understanding (covered below).

What is a good running pace?

“Good” pace depends entirely on context — a 10 min/mile pace is a very common, perfectly respectable pace for most healthy adults running regularly, while the same pace would be a recovery jog for a competitive amateur. Rather than comparing to a generic benchmark, a widely-used practical guide for easy/aerobic running is the “talk test”: if you can hold a conversation in full sentences without gasping, you’re at a sustainable aerobic pace appropriate for building a base, regardless of what that pace number happens to be for your fitness level.

Pace also naturally varies by distance for the same runner — most people run a 5K meaningfully faster per mile than a marathon, since a shorter race allows a higher sustained intensity that couldn’t be maintained over 26.2 miles without running out of glycogen stores or accumulating too much fatigue. This is sometimes summarized as “you can’t sprint a marathon,” and it’s part of why comparing pace across different race distances for the same person isn’t a like-for-like comparison — a 7:30/mile 5K pace and an 8:30/mile marathon pace could represent a very similar level of fitness and effort, just applied to different race lengths.

Converting between units

The 1.609344 figure is the internationally defined exact conversion between miles and kilometers (1 mile = 1.609344 km precisely) — this calculator uses that exact figure rather than a rounded approximation, so conversions stay accurate even for longer distances where small rounding errors would otherwise compound. A 10:00/mile pace converts to almost exactly 6:13/km; a 6:00/km pace converts to about 9:39/mile.

Pace for common race time goals

These figures come directly from Time ÷ Distance for the full marathon distance (26.2188 miles) — the same calculation this tool runs in “Find Pace” mode. Working backward from a target finish time to a required pace is one of the most common practical uses of a pace calculator: entering the marathon distance with a goal time in “Find Pace” mode shows exactly what average pace needs to be held for the full 26.2 miles to hit that target.

The same approach works for any race distance and any goal time, not just the marathon benchmarks above — a runner targeting a specific half marathon, 10K, or 5K goal can enter that exact distance and target time in “Find Pace” mode to get the precise pace needed, rather than relying on a generic lookup table. This is particularly useful for less commonly-referenced goal times (a 1:52 half marathon, for instance) where a pre-built pace chart is unlikely to have the exact number readily available.

Why pace isn't perfectly even in practice

The pace this calculator computes is an average across the full distance — real races and training runs rarely happen at a perfectly flat pace throughout, even for well-paced efforts. Course terrain (hills, turns, surface changes), pacing strategy (a slight negative split, running the second half faster than the first, is a commonly recommended race strategy), fatigue in the later stages of longer races, and even weather and course crowding all cause real pace to vary mile to mile around that average. This is a normal and expected part of running, not a sign that a plan has failed — the average pace this calculator computes remains the correct number to plan around and compare against, even though no individual mile will match it exactly. Runners tracking splits mile-by-mile are comparing against this average specifically to see where they’re running ahead of or behind the pace needed for their target time, which is a more useful signal than expecting every single mile to be identical.

A negative split — running the second half of a race faster than the first — is worth calling out specifically, since it’s one of the most consistently recommended pacing strategies in distance running, backed by analysis of elite race results showing that even-paced or negative-split efforts tend to outperform races that start fast and fade. Starting a race at or slightly below goal pace, even though it can feel conservative early on when everyone around you surges ahead, is one of the most reliable ways to protect against the severe late-race slowdown that an overly fast start tends to produce.

Using pace to plan training

Training plans commonly reference pace relative to race pace rather than as an absolute number, since this scales appropriately to any runner’s fitness level: easy runs are often prescribed at 60–90 seconds per mile slower than goal race pace, tempo runs closer to or slightly slower than goal pace, and interval work faster than goal pace for shorter repeated segments. Using this calculator to first establish an accurate goal race pace (from a target finish time and race distance) gives a concrete anchor number that the rest of a training plan’s paces can be built from.

For runners without a specific goal race yet, working the calculator in reverse — entering a recent training run’s distance and time to find current pace — establishes a realistic present-fitness baseline, which is generally a more reliable starting point for setting a race goal than picking a time first and hoping the fitness follows.

Recovery runs deserve a specific mention, since they’re often the pace runners are least disciplined about. A true recovery run — typically 90 seconds to 2 minutes per mile slower than easy pace — is meant to promote blood flow and active recovery without adding meaningful additional training stress, and running it too fast defeats its purpose without adding a meaningful fitness benefit in return. Using this calculator to check that a recovery run’s actual pace falls into the intended slow range, rather than trusting perceived effort alone (which tends to drift faster over time as fitness improves), is a simple way to keep an easy day genuinely easy.

mph vs. pace — which to use

Pace (minutes per mile or km) is the standard unit among runners for a practical reason: it maps directly onto how races are experienced and split — checking a watch at each mile marker and comparing to a target pace is far more intuitive during a run than doing mental math with a speed figure. Cyclists and some treadmill displays default to mph or km/h instead, largely because speed is the more natural unit at higher speeds where pace-per-mile would be under a minute and harder to read meaningfully.

Both describe exactly the same underlying effort — this calculator shows both simultaneously specifically so the conversion never has to be done by hand, whether comparing a treadmill’s mph display against a race-pace goal, or converting a cycling computer’s speed reading into a more intuitive per-mile or per-km pace figure for a comparison.

One practical use for the mph figure specifically: most treadmills are set by speed (mph or km/h) rather than pace, so knowing the mph equivalent of a goal race pace makes it possible to replicate that exact effort on a treadmill for a workout, rather than approximating it. Since treadmill belts run at a fixed, precisely controlled speed — unlike outdoor running, where pace naturally drifts with terrain, wind, and fatigue — a treadmill set to the correct mph is actually one of the more reliable ways to practice holding an exact goal pace for an extended period before race day.