Do The Impossible
A suite of precision tools designed to help you calculate, track, and optimize your performance limits.
Free training calculators
Impossible Fitness tools do the math so you can spend your energy on the work itself. Every calculator is free, runs in your browser and doesn't need an account.
The 1-rep max calculator estimates your one-rep max from any set of 1 to 10 reps, so you can program heavy days without testing a true max. The percentage chart turns that number into working weights for sets at 50–100%, and the plate calculator tells you exactly which plates go on each side of the bar.
For conditioning, the heart-rate zones calculator sets your five training zones, and the running calculator converts between pace, time and distance for anything from a 400m repeat to a marathon. The macro calculator sets daily protein, carb and fat targets for losing fat, maintaining or building muscle.
Pair them with the movement library and our benchmark WODs to plan, load and track your training.
Macro Calculator
Calculate BMR, TDEE, and exact nutrient splits for fat loss or muscle gain.
Launch ToolRunning Calculator
Predict your marathon, half-marathon, and 5k times based on recent performance.
Launch Tool1-Rep Max
Calculate your theoretical strength limits safely without maxing out.
Launch ToolPercentage Chart
Generate a printable percentage grid for weightlifting based on your 1-Rep Max.
Launch ToolPlate Calculator
Quickly calculate exactly which plates to load on the bar for any weight.
Launch ToolHR Zones
Optimize your endurance training by calculating your specific heart rate zones.
Launch ToolThe Impossible Family
⚠️ Disclaimer: These calculators are for informational purposes only and not medical advice. Consult a physician before starting any new diet or exercise program.
By using these tools, you assume all risks and agree that Impossible Fitness is not liable for any injuries or health issues.