Running Pace Calculator

How Running Pace Calculator Works

Pace, distance, and finish time are all locked together by one relationship -- knowing any two always determines the third. This calculator solves for whichever one you're missing: figure out your finish time for a race at a target pace, the pace you need to hit a goal time, or how far you'd get running a known pace for a known duration.

Formula & Method

The three modes all come from the same identity, Finish Time = Pace × Distance, just solved for a different variable each time: Finish Time mode multiplies pace (seconds per unit) by distance; Pace mode divides finish time by distance; Distance mode divides finish time by pace. Everything is computed internally in seconds and converted to minutes:seconds or hours:minutes:seconds only for display. Switching between km and miles converts your currently entered distance and pace on the spot (using 1 mile = 1.609344 km), so changing units mid-calculation doesn't silently reinterpret your numbers under the new unit.

Worked Example

A 5K at a 5:00/km pace gives a finish time of exactly 25:00 (5 minutes × 5 km), a speed of 12 km/h, and an equivalent pace of about 8:03/mile.

Frequently Asked Questions

Why does switching units convert my numbers instead of just relabeling them?

A pace or distance value means something completely different under a different unit -- "5:00 per km" and "5:00 per mile" are two different speeds. Converting the actual numbers when you switch preserves the pace and distance you actually meant, rather than silently treating your km numbers as if they were miles.

What are the race distance presets based on?

They're the standard official distances for common road races: 5K and 10K are exact metric distances, while Half Marathon (21.0975 km / 13.10938 mi) and Marathon (42.195 km / 26.21875 mi) are the official distances set by World Athletics, not rounded approximations -- useful for plugging in a real target pace for an actual race distance.

How is "speed" different from "pace"?

They're two ways of expressing the same rate -- pace is time per unit distance (e.g., minutes per km, the way runners usually think about effort), while speed is distance per unit time (e.g., km per hour, the way it's usually described in general conversation or on a treadmill display). The calculator shows both so you can use whichever framing you need.

Can I use this for a treadmill workout, not just a race?

Yes -- the same math applies regardless of context. If your treadmill displays speed rather than pace, converting via the speed stat this tool shows lets you match a treadmill setting to a target race pace, or vice versa, without doing the mph-to-min/km conversion by hand.