Running Pace Calculator
Fill in any two of distance, time, or pace — we’ll solve for the third.
Pace as a training tool
Different paces train different systems. Easy runs build your aerobic base and mitochondrial density. Tempo runs build lactate threshold. Intervals build VO2 max. Mixing them intentionally produces far better results than just running 'how you feel' at whatever pace emerges.
The 80/20 rule: roughly 80% of weekly mileage should be easy (conversational pace, 60–75% max HR), 20% hard. Most amateur runners flip this ratio and wonder why they plateau or injure. Slower easy days fuel faster hard days — counterintuitive but well-established.
Frequently asked questions
How do I use pace for training?
Different paces train different systems. Easy pace (conversational, 60–70% max HR) builds aerobic base — do 80% of your volume here. Tempo pace (comfortable-hard) builds lactate threshold. Interval pace (5K race pace or faster) builds VO2max. Most injuries come from running easy days too fast.
How much slower than race pace should easy runs be?
60–90 seconds per mile slower than 5K race pace is the usual guideline. Many experienced runners hit 'easy' around 2 min/mile slower than marathon pace. If you can't hold a conversation, you're running too fast.
What's the McMillan calculator doing?
Using your time in one race distance to predict equivalent efforts at other distances, based on empirical running data. It's best for similar distance ranges (5K to 10K) and less reliable across big gaps (5K to marathon) because training-specific endurance matters more than raw speed over long distances.
How do heat and hills affect pace?
Add ~10–20 sec/mile for each 10°F above 60°F. Add ~15 sec/mile per 1% grade uphill; subtract only ~8 sec/mile per 1% downhill (descents aren't free — they beat up quads). Adjust training paces in heat and on hilly courses to preserve effort consistency.
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