Which formula is used here?

Converts a known distance and time into pace metrics, then projects race times using constant pace assumptions.

Can I use metric or imperial units?

Yes. This tool supports both metric and imperial units and remembers your preference.

Is this medical advice?

No. This tool provides general fitness estimates and should not replace medical guidance.

Is this tool free and private to use?

Yes. AI Fit Hub tools are free, no-signup browser tools. Inputs stay in your browser unless you choose to share a URL.

Do these tools replace medical guidance?

No. These outputs are general fitness estimates — not medical advice.

Can I switch between metric and imperial units?

Yes. Every tool supports both systems and remembers your preference in localStorage.

Methodology: Running Pace Calculator

Scope

Converts between time, distance, and pace; projects finish times across standard race distances.

Formula

pace = time / distance. finish_time = pace * distance.

Coefficients

Parameter	Value	Note
5K distance	`5.000 km`
10K distance	`10.000 km`
Half marathon	`21.0975 km`
Marathon	`42.195 km`

Data sources

World Athletics — Road Running Measurement procedures. — Federation rulebook for certified-course measurement and standard race distances.
USA Track & Field — Course Certification Program. — U.S. governing body for road race course certification.
Daniels JT. Daniels' Running Formula. 4th ed. Champaign, IL: Human Kinetics, 2021. — Source for the VDOT-based pace projection methodology used in projecting finish times across distances.

Assumptions

Course is measured accurately; GPS watches typically over-report distance by 1–2%.

Approximation range

The arithmetic is exact. Residual error lives in distance measurement and GPS drift.

Limitations

Ignores elevation, wind, and terrain.

Reproducibility

10 km in 50:00. Pace = 50/10 = 5:00/km. Half-marathon projection at same pace: 5:00 * 21.0975 = 1:45:29.

Change log

2026-04-24: methodology page first published.

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Worked example

Computed by the same engine bundle served at /engines/running-pace-calculator.js. Re-runnable: the values below are the literal output of compute(engineInput).

Input

tool: running_pace_calculator
distance_km: 10
time_minutes: 50

Output

paceMinPerKm: 5
paceMinPerMile: 8.04672
projectedRaces: [{"label":"5K","distanceKm":5,"timeMinutes":25},{"label":"10K","distanceKm":10,"timeMinutes":50},{"label":"Half Marathon","distanceKm":21.0975,"timeMinutes":105.4875},{"label":"Marathon","distanceKm":42.195,"timeMinutes":210.975}]

FAQ

Which formula is used here?: Converts a known distance and time into pace metrics, then projects race times using constant pace assumptions.
Can I use metric or imperial units?: Yes. This tool supports both metric and imperial units and remembers your preference.
Is this medical advice?: No. This tool provides general fitness estimates and should not replace medical guidance.
Is this tool free and private to use?: Yes. AI Fit Hub tools are free, no-signup browser tools. Inputs stay in your browser unless you choose to share a URL.
Do these tools replace medical guidance?: No. These outputs are general fitness estimates — not medical advice.
Can I switch between metric and imperial units?: Yes. Every tool supports both systems and remembers your preference in localStorage.