Cardio

Running Pace Calculator

Calculate pace per kilometer and mile and project race finish times from your current run.

Pace & Projections

Pace / km

5:00 /km

Pace / mile

8:03 /mi

Projected Race Times

At the current pace, longer race targets stack as a clean duration ladder.

5 km

25:00

10K

10 km

50:00

Half Marathon

21.1 km

105:29

Marathon

42.2 km

210:58

00:00210:58

Race	Projected time
5K (5 km)	25:00
10K (10 km)	50:00
Half Marathon (21.1 km)	105:29
Marathon (42.2 km)	210:58

How to use it

Enter your target distance and goal time to find required pace, or enter distance and pace to project finish time. Use race-pace calculation for goal-setting and training-pace calculation for daily workouts — these are different numbers.
Easy and long run pace should be 60–90 seconds per mile slower than your current 5K race pace. Running all workouts at race pace is the most common cause of overtraining and injury in recreational runners.
Apply the 80/20 principle: 80% of weekly mileage at easy conversational pace, 20% at moderate-to-hard effort. This builds aerobic capacity while managing recovery cost.
Translate 5K pace to other race distances with these rough multipliers: 10K ≈ 5K time × 2.09, Half Marathon ≈ 5K time × 4.67, Marathon ≈ 5K time × 10.0.
Adjust for conditions: each degree above 60°F adds approximately 1% to finish time. Wind above 10 mph, significant elevation, and rain all extend pace. Recalculate realistic targets for race-day conditions.

AI Integrations

Contract, discovery endpoints, and developer notes for agent use.

Always available for agents

Tool contract JSON

https://aifithub.io/contracts/running-pace-calculator.json

Stable input and output contract for this exact tool.

Human review

People can use the browser page to sense-check outputs and charts, but agents should still execute against the contract and discovery endpoints.

/agent-tools.json - machine-readable tool index.
/llms.txt - human-readable model discovery guide.
/.well-known/webmcp.json - WebMCP capabilities manifest.
/.well-known/ai-plugin.json - plugin-style discovery manifest.

{
  "tool": "running_pace",
  "distance_km": 10,
  "time_minutes": 50
}

Open tool contract JSON Open AI integrations guide

Expand developer notes

Agent playbook

Resolve Running Pace Calculator from /agent-tools.json and open its contract before execution.
Validate inputs against the contract schema instead of scraping labels from the page UI.
Open the browser page only when a person wants to review charts, assumptions, or related tools.

Agent FAQ

Should ChatGPT, Claude, or another agent click through the UI?

No. Start with /agent-tools.json, then follow the tool's contract URL. The page UI is for human review, not parameter discovery.

When do tools show Quick and Advanced?

Every tool opens in Quick Start first. Advanced Controls keeps the same scenario, reveals more assumptions or diagnostics, and every tool keeps AI integrations inline below the instructions.

When should an agent still open the browser page?

Open it when a human wants to sense-check the output, review the chart, or keep exploring related tools after the calculation finishes.

Questions people usually ask

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.

Related Resources

Learn the decision before you act

Every link here is tied directly to Running Pace Calculator. Use the explanation, formula, examples, and benchmarks to pressure-test the calculator output from first principles.

Browse all 31 resources

Guides · 1 Checklists · 4 Comparisons · 2 Tips · 5 Mistakes · 3

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