One Rep Max Calculator
Enter a weight and the reps completed, and the calculator estimates a one rep max using the average of the Epley and Brzycki equations, then builds a percentage-based loading table you can program from immediately. It works in pounds or kilograms and rounds every load to a real plate increment, because a prescription of 183.7 lb helps nobody on the floor.
How the estimate works
The calculator averages two of the most widely used prediction equations. Epley estimates 1RM as weight x (1 + reps / 30), while Brzycki estimates it as weight x 36 / (37 - reps). The two formulas agree closely between 2 and 6 reps and drift apart as reps climb, which is why averaging them gives a steadier number across the usable range. Both equations lose accuracy above about 10 reps, so if you are testing to anchor a training block, a heavy set of 3 to 5 gives you a far more reliable estimate than a set of 12 taken to failure.
From one estimate to a full roster
A calculator solves the problem for one athlete on one lift. The real workload shows up when you are tracking maxes for 60 athletes across squat, bench, and clean, updating them after every testing block, and writing programs that prescribe from those numbers automatically. That is the job FYTT's Metrics Hub does: you define the metrics your program actually tests, FYTT stores every athlete's current values, and your program templates prescribe loads as percentages that resolve to each athlete's own numbers. When a max changes, every downstream prescription updates with it, which means the spreadsheet you currently rebuild after testing week simply stops existing.
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Frequently asked questions
How accurate are 1RM calculators?
Accurate enough to program from, within limits. Prediction equations like Epley and Brzycki typically land within a few percent of a true max when the estimate comes from a set of 2 to 6 reps, and the error grows as reps increase. Accuracy also varies by lift and training age, since well-trained athletes tend to grind out more reps at a given percentage than novices. Treat the output as a planning anchor you refine with training data, not a substitute for testing.
What rep range gives the best 1RM estimate?
Sets of 2 to 6 reps give the most reliable estimates. Below that you are just testing a true max, and above roughly 10 reps the relationship between reps and load flattens out, so small differences in rep count swing the estimate widely. If you want a useful estimate without testing a true single, a heavy triple is the standard choice.
Should athletes test a true 1RM or use an estimate?
It depends on the athlete and the calendar. True max testing gives the cleanest number but carries more fatigue and more risk, which is hard to justify in-season or with younger athletes. Most college and high school programs test rep maxes and estimate, then reserve true max attempts for trained athletes at the end of a dedicated strength block. Either way, the number only matters if it feeds the next block's prescriptions.
How do coaches use 1RM percentages in programming?
Percentages translate one tested number into every prescription in a block. A coach assigns, for example, 5x5 at 75% in a strength phase, and each athlete's working load resolves from their own max. In FYTT, those percentages live in the program template and resolve automatically from each athlete's current values in Metrics Hub, so the same template serves the whole roster without anyone touching a calculator or a spreadsheet.
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Upgrade Your Strength and Conditioning System
Join 50+ performance organizations using FYTT to automate programming, individualize training, and apply sport science at scale.
No credit card required. Cancel anytime.
2701 N Thanksgiving Way
Ste 100
Lehi, UT, 84043
Call: +1 618 200 7011
Text: +1 833 370 7084
2701 N Thanksgiving Way
Ste 100
Lehi, UT, 84043
Call: +1 618 200 7011
Text: +1 833 370 7084
2701 N Thanksgiving Way
Ste 100
Lehi, UT, 84043
Call: +1 618 200 7011
Text: +1 833 370 7084