Calculate Your Half Marathon Training Paces From a Recent Race

Your plan tells you to run at "threshold" or "easy" pace, but nobody's told you what that actually means in minutes per mile. Base every training pace on a race you've actually run in the last 6-8 weeks, not the time you hope to run on race day. A goal time tells your paces what you want; a recent result tells them what your body can currently do. Training off the wrong one leads to blown-up long runs and missed workouts. Most calculator tools online skip the explanation entirely. Here's the method, with a full worked example.

Get that starting number wrong and every session downstream inherits the error — you'll spend weeks either sandbagging tempo runs that should be pushing you, or grinding long runs at a pace that's quietly digging a hole before taper. Fix the input once and the rest of your training stops guessing.

Which Race Distance Predicts Half Marathon Paces Best

Not every recent race predicts equally well. A recent half marathon, run within the last 8 weeks, is the single best predictor — no adjustment needed. A 10K is the next best option: add roughly 12-15 seconds/mile to your 10K race pace to estimate half marathon race pace.

A 5K is usable but least reliable for the half specifically — its prediction skews faster than your actual half fitness if you're less aerobically developed. Treat any 5K-derived number as a ceiling estimate, not a target.

Worked Example: One Race Time, Three Training Paces

No ranking page walks through an actual number, so here's mine. Take a 55:00 10K. That converts to a half marathon race pace of roughly 9:00-9:15/mile.

This is the exact pace-conversion tool I use with athletes before assigning training paces — one input number, three usable outputs.

Easy Pace: Wider Than You Think

Easy pace is a 60-90 second/mile band, not a fixed number. Conversational effort — the ability to speak in full sentences — is the real test. The number is a guardrail, not the goal.

Tempo Pace: Between 10K and Half Marathon Effort

Tempo, or threshold, pace sits roughly 15-25 seconds/mile faster than half marathon race pace and 10-15 seconds/mile slower than your current 10K race pace. It should feel comfortably hard — not all-out.

No Recent Race? Time-Trial and Effort-Based Alternatives

I'd rather an athlete run an honest 2-mile time trial than train off a 5K they ran fresh eight months ago — recency beats distance-accuracy every time. Warm up 10 minutes, run 2 miles at maximum sustainable effort, cool down, then plug that result into the same 10K-equivalent maths above.

If you'd rather not time-trial, use an effort-based fallback: RPE 3-4/10 for easy pace, RPE 6-7/10 for tempo pace.

Recalibrating Your Paces Mid-Training-Block

Re-test every 4-5 weeks during a 12-16 week block, either via a tune-up race or the same 2-mile time trial. If the new number is more than 10-15 seconds/mile faster, update all three training paces — don't wait until the final taper to discover your paces are stale.

Athletes who refuse to update paces mid-block consistently show up to taper week either overcooked, from training too hard on stale-slow numbers, or undercooked, from sandbagging an early-block estimate.

Frequently Asked Questions

Which race distance predicts half marathon training paces best?

A recent half marathon, run within the last 8 weeks, is the single best predictor — no adjustment needed. A 10K is the next best option, adding roughly 12-15 seconds/mile to your 10K race pace. A 5K is usable but least reliable, since it tends to skew faster than your actual half marathon fitness.

What if my only recent race was a 5K?

You can still use it, but treat any 5K-derived half marathon pace as a ceiling estimate, not a target. It tends to skew faster than what's sustainable over 13.1 miles, especially for less aerobically developed runners.

How old can a "recent" race be to use for pace calculations?

6-8 weeks is the useful window. Beyond that, your fitness has likely shifted enough that the number stops reflecting what your body can currently do, especially if you've been training consistently since.

What if I have no recent race at all?

Run a structured 2-mile time trial — warm up 10 minutes, run 2 miles at maximum sustainable effort, cool down — and plug that result into the same 10K-equivalent maths. If you'd rather not time-trial, use effort-based guides instead: RPE 3-4/10 for easy, RPE 6-7/10 for tempo.

Should I use my goal time or my current race time to set training paces?

Your current time, always. A goal time tells your paces what you want; a recent result tells them what your body can currently do. Training off the wrong one leads to blown-up long runs and missed workouts.

How much slower is easy pace than tempo pace?

Easy pace typically sits 75-90 seconds/mile slower than half marathon race pace, while tempo sits 15-25 seconds/mile faster than race pace. That gap between the two is usually 90-115 seconds/mile.

What if my calculated paces feel wrong in practice?

Trust effort over the number for a session or two, then reassess. Conversational effort is the real test for easy pace; comfortably hard is the real test for tempo. If the mismatch persists past 2 sessions, your input race time may be stale — consider recalibrating.

How often should I recalculate my paces mid-plan?

Re-test every 4-5 weeks during a 12-16 week block, via a tune-up race or the same 2-mile time trial. If the new number is more than 10-15 seconds/mile faster, update all three training paces rather than waiting until taper to discover they're stale.

Should I adjust my paces for heat, altitude, or the treadmill?

Yes — treat your calculated paces as flat, cool-weather, sea-level numbers. Add roughly 3-5 seconds/mile per 5°F above 60°F, adjust upward for altitude, and use effort rather than pace on a treadmill until you've calibrated the display against outdoor runs.

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