Tools Field Notes Gear About
Tool No. 01

Average Pace
Calculator

Log your splits as you run and instantly see exactly what pace you need for the remaining miles to hit your target average. Whether you're fading at mile 8 of a half marathon or pushing for a negative split in a full, this tool gives you real-time adjustments so you can finish strong.

Race Info
: /mi
Logged Splits
Current Average Pace
--:-- /mi
Required Pace by Remaining Distance
How It Works
Real-Time
Pace Math

Most runners check their watch at mile markers and do rough mental math — "I'm a little fast, I'll back off." That works fine until you've gone out too hard and need to know exactly how much damage has been done.

This tool calculates it precisely: Required pace = (Goal total time − Time already elapsed) ÷ Miles remaining. Log each mile split as you go and the required pace projection updates instantly for every remaining distance — 1 mile out, 5K out, all the way to the finish.

Built specifically for mid-race use. Large number inputs, number pad on iOS, and a single-tap edit flow so you can update splits with gloves on or at mile 9 when your hands are less cooperative than usual.

Common Questions
To finish a half marathon in under 2 hours, you need to average faster than 9:09 per mile across all 13.1 miles. A safe target is 9:00/mi — giving you a small buffer for hills, crowding, and the inevitable slowdown in the final miles. Use this calculator to adjust in real time if your early splits come in faster or slower than planned.
The formula is: Required pace = (Goal total time − Time already spent) ÷ Miles remaining. In practice this is hard to compute mid-run. That's what this tool does — enter your goal pace and logged splits, and it shows you the exact required pace for every remaining mile distance in real time.
Negative splits means running the second half of a race faster than the first. It's the pacing strategy used by nearly every elite runner in distance events. Going out conservatively allows you to run faster when others are fading — most runners who blow up in the final miles ran their first miles too fast. This calculator shows you exactly when you're ahead or behind a negative split pace.
Running the first mile 30 seconds per mile too fast can cost you 2–4 minutes in the final 5K as glycogen depletion and lactate accumulation compound. The physiological debt is disproportionate to the time "banked" early. Research on marathon pacing consistently shows the fastest finishing times come from even or slightly negative splits — not from banking time at the start.
Yes. The calculator supports 5K, 10K, half marathon, full marathon, and custom distances. Select your race distance from the dropdown, enter your goal pace, and log splits as you complete each mile. The required pace projection updates automatically for whatever distance you've selected.
For a first half marathon, anywhere between 10:00 and 12:00 per mile is a solid finishing pace depending on your training base. A 10:00/mi pace finishes in about 2:11. A 12:00/mi pace finishes in about 2:37. The goal for a first half should be finishing strong — start conservatively at a pace that feels almost too easy for the first four miles.
Field Note
Why Your First Mile Is Lying to You — the physiological and psychological reasons your opening pace can't be trusted.
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