Pick Your Calculator
VDOT Calculator
Enter a recent race result and get your VDOT score plus precise training paces for Easy, Marathon, Threshold, Interval, and Repetition runs — in min/km and min/mile.
Open VDOT Calculator →Marathon Pace Calculator
Convert any marathon goal time into the exact pace you need to hold — plus full per-km and per-mile split tables for even and negative-split strategies.
Open Pace Calculator →Race Time Predictor
Plug in one race result. Get predicted times for 1 mile, 5K, 10K, 15K, 10 mile, half marathon, marathon, and 50K — using both Riegel and Cameron formulas.
Open Race Predictor →80/20 Training Calculator
Built on Stephen Seiler's polarized training research. Enter your weekly mileage and get a balanced schedule with the right easy/hard split for your goal race.
Open 80/20 Calculator →Training Load Calculator
Compute your acute:chronic workload ratio — the metric Tim Gabbett's research links to injury risk. Find your sweet spot, avoid the injury-risk zone.
Open Load Calculator →Why we built these
Most "running calculators" online are 10-year-old pages buried in ads. The math is right but the experience is awful, and they rarely link to each other in a way that helps you actually train better.
We're the team behind The Running Genie — an AI marathon coach that does this math automatically every day. We pulled the same formulas out into five focused, fast, ad-free pages so anyone can use them, even if they never download the app.
How the calculators connect
The five tools are designed to work together. A typical workflow looks like this:
- Step 1 — Find your fitness: Run the VDOT calculator with a recent race. This gives you a single number that quantifies your aerobic fitness.
- Step 2 — Set a goal: Use the race time predictor to see what your VDOT predicts at the marathon distance. Pick a realistic goal time.
- Step 3 — Plan your race execution: Plug your goal into the marathon pace calculator for split-by-split pacing.
- Step 4 — Plan your week: Use the 80/20 calculator to lay out the right balance of easy and hard runs.
- Step 5 — Stay healthy: Track your weekly load with the training load calculator to keep your ACWR in the sweet spot and avoid injury.
What's the catch?
There isn't one. The calculators are static HTML — your numbers never leave your browser. We pay for the hosting because runners who like the tools sometimes try the app, and a small fraction become paying users. That's the deal.
Frequently Asked Questions
Are these running calculators free?
Yes — all five calculators are completely free, run entirely in your browser, require no sign-up, and don't store your inputs. They're built and maintained by the team behind The Running Genie marathon training app.
Which calculator should I use first?
Start with the VDOT calculator if you've raced recently — it gives you a single fitness number that drives every training pace. Use the race time predictor if you want to see what your current 5K could mean for the marathon. Use the 80/20 calculator to plan your weekly mileage split, and the training load calculator to keep injury risk low while building fitness.
Are the formulas the same as Jack Daniels' tables?
The VDOT calculator uses the standard Daniels VO2/velocity equations from the Daniels Running Formula. Results match the published VDOT tables to within rounding. The race time predictor uses Pete Riegel's formula plus a Cameron-style correction for longer distances; the marathon prediction also accounts for training experience.
Do these calculators work on mobile?
Yes. Every calculator is mobile-first and uses numeric input modes so iOS and Android phones show the right keyboard. They run as static pages with no external dependencies and load fast on slow connections.
Where do these tools fit alongside The Running Genie app?
The calculators are useful one-off tools — plug in numbers, get an answer. The Running Genie app does the same math automatically every day, then turns it into a 16-week adaptive training plan that updates as your fitness changes. If you find yourself running these calculators every week, the app will save you that work.
Do you save my inputs?
No. Every calculator runs entirely in your browser. We don't post your numbers to a server, don't tie them to an account, and don't share them with anyone. Standard analytics (Google Analytics, PostHog) record page views and clicks but not the values you type.
Can I link to these from my running club / training plan?
Please do. The pages are stable URLs and we won't break them. If you find an issue or want a calculator we don't have yet, reach out — we add tools based on what runners actually ask for.
All of this, automatically — every day.
The Running Genie runs your VDOT, training paces, 80/20 split, and ACWR continuously from your runs — and turns the math into a 16-week adaptive marathon plan. Free download, no credit card to start.
