One Rep Max Calculator
What is One Rep Max Calculator
A one-rep max (1RM) is the heaviest weight you can lift for a single rep. This calculator estimates it from a set you already did, so you never have to grind out a risky max attempt. Enter the weight and how many reps you hit, and it runs the Epley, Brzycki and Lombardi formulas, averages them for a headline number, and lays out the load for every rep count from 1 to 10.
How to use
- Pick your unit, kilograms or pounds.
- Enter the weight you lifted.
- Enter how many clean reps you completed.
- Read your estimated 1RM and the per-formula breakdown.
- Use the percentage table to set loads for your working sets.
When to use it
Squatted 100 kg for 5 solid reps and want your true max? Enter 100 and 5 and you get about 116 kg, with the percentage table showing 90 kg for a set of 10 and 110 kg for a triple. Handy for programming a strength block, checking progress without testing a true max, or picking the right load for a given rep target.
Frequently asked questions
How is one-rep max calculated?
It uses prediction formulas that relate the weight you lifted to the reps you did. This tool runs three of the best-known ones, Epley, Brzycki and Lombardi, and averages them so no single formula's bias skews the result.
Which 1RM formula is most accurate?
No formula is perfect, and they diverge as reps climb. Epley and Brzycki track closely at low reps and are the most widely used, while Lombardi holds up a bit better at higher reps. Averaging all three, as this tool does, is a reasonable middle ground.
How many reps should I use for the best estimate?
Fewer is better. Estimates are most reliable at 10 reps or fewer, and a set of 3 to 5 near failure gives the sharpest prediction. Above 10 reps, endurance and technique start to matter more than raw strength, so the numbers drift.
Is it safe to lift my estimated 1RM?
Treat it as a theoretical ceiling, not a target for today. It assumes a fresh, well-warmed lifter with solid form and, ideally, a spotter. Build up to any true max attempt gradually rather than jumping straight to the estimate.
Can I share this tool with my inputs pre-filled?
Yes. The URL updates automatically as you type. Copy it from the address bar or use the Copy link button, and anyone who opens the link will see your exact inputs ready to go.
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