Pick Your Calculator
Running Pace Calculator
Enter any two of distance, time, or pace and solve the third — for any distance. Get a split table and equivalent 5K, 10K, half, and marathon finish times.
Open Pace Calculator →Heart Rate Zone Calculator
Enter your age — and optional resting heart rate — to get all five training zones in beats per minute, using the %HRmax or Karvonen method.
Open HR Zone Calculator →Treadmill Pace Converter
Convert treadmill speed to pace in min/km and min/mile, and adjust for incline to see your equivalent outdoor effort.
Open Treadmill Converter →Running Calorie Calculator
Estimate calories burned running from your weight, distance, and time — with an incline option — using the ACSM metabolic equation.
Open Calorie Calculator →Yasso 800s Calculator
Turn your marathon goal into Yasso 800 repeat times — with pace per km and mile and the full 10 × 800m workout.
Open Yasso 800s Calculator →Run/Walk Calculator
Find your average pace and finish time for any run/walk interval ratio — enter your run and walk intervals and paces.
Open Run/Walk Calculator →Sweat Rate Calculator
Weigh in before and after a run to find your sweat rate per hour, dehydration percentage, and how much to drink.
Open Sweat Rate Calculator →Weekly Mileage Calculator
Build a safe week-by-week mileage progression with the 10% rule, and see how long it takes to reach your goal volume.
Open Mileage Calculator →Race Fueling Calculator
Enter your finish time to get carbs per hour, total carbs, how many gels to carry, and when to take them.
Open Fueling Calculator →VO2 Max Calculator
Estimate your VO2 max from a Cooper 12-minute run test or from your resting and maximum heart rate.
Open VO2 Max Calculator →Cadence & Stride Length Calculator
Enter any two of pace, cadence, and stride length to solve the third — with step and stride length in metres and feet.
Open Cadence Calculator →Steps to Distance Calculator
Convert steps to miles and kilometres and back, from your step length or an estimate based on your height.
Open Steps Calculator →Carb Loading Calculator
Work out how many grams of carbohydrate to eat per day when loading before a marathon or long race, from your body weight.
Open Carb Loading Calculator →Track Interval Pace Calculator
Turn a goal pace or race time into 200m–1600m rep split times, plus your per-400m lap time.
Open Interval Calculator →Negative Split Calculator
Get your first-half and second-half paces and halfway split for any goal time, distance, and split differential.
Open Negative Split Calculator →Grade-Adjusted Pace Calculator
Convert a pace run on a hill to its flat-ground equivalent effort, or find the pace to run on any incline.
Open GAP Calculator →Heat Pace Calculator
Estimate how much a hot day slows your running — adjusted pace, percentage slowdown, and time lost over a race.
Open Heat Pace 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.
