One Rep Max Calculator
Calculate your estimated one-rep maximum based on weight and reps performed
What is a one rep max (1RM) and how is it calculated?
A one rep max (1RM) is the maximum weight you can lift for a single repetition. It's estimated using formulas like Epley: 1RM = Weight × (1 + Reps/30). For example, if you bench press 80kg for 8 reps, your estimated 1RM is about 101kg. Use 1RM percentages to plan training loads for strength, hypertrophy, or endurance.
(1-12 reps recommended for accuracy)
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Create Free AccountWhat is One Rep Max?
One Rep Max (1RM) is the maximum amount of weight you can lift for a single repetition with proper form. It's a key metric in strength training used to measure progress, plan training programs, and determine appropriate working weights. Knowing your 1RM allows you to train at specific percentages for different goals - strength, hypertrophy, or endurance.
1RM Formulas Explained
Several formulas estimate your 1RM from submaximal lifts. The Epley formula (1RM = weight × (1 + reps/30)) works best for 6-10 reps. The Brzycki formula (1RM = weight × 36/(37-reps)) is more accurate for lower rep ranges (1-6). The Lander formula provides a good middle ground. All formulas become less accurate above 10-12 reps. For best results, use a weight you can lift for 3-6 reps with good form.
How to Use Your 1RM
Once you know your 1RM, you can plan training loads effectively. For maximum strength (1-5 reps), work at 85-100% of 1RM. For strength and size (6-8 reps), use 75-85%. For hypertrophy (8-12 reps), use 65-75%. For muscular endurance (12-15+ reps), use 50-65%. Remember that these are estimates - always prioritize proper form and use a spotter for heavy lifts.
Frequently Asked Questions
How accurate are 1RM calculators?
1RM calculators are most accurate when using 3-6 reps at a heavy weight. Accuracy decreases significantly above 10 reps. The Brzycki formula tends to be most accurate for low reps (1-6), while the Epley formula works better for moderate reps (6-10). For best results, test with a weight you can lift for 3-5 reps with proper form.
Should I actually attempt my calculated 1RM?
Only attempt a true 1RM if you have experience with heavy lifting, proper form, and a trained spotter. For most training purposes, using calculated percentages of your estimated 1RM is safer and equally effective for programming. Many successful strength programs never require true maximal attempts.
How often should I test or recalculate my 1RM?
Recalculate your estimated 1RM every 4-8 weeks as you progress. This aligns with typical training cycles and ensures your working weights stay appropriately challenging. You can simply input your latest heavy set into the calculator rather than attempting a true 1RM test.
What percentage of 1RM should I train at?
For maximum strength, train at 85-95% of 1RM for 1-5 reps. For strength and size, use 75-85% for 5-8 reps. For hypertrophy (muscle growth), use 65-75% for 8-12 reps. For muscular endurance, use 50-65% for 12-20 reps. Most people benefit from varying percentages across their training week.
Why do different formulas give different results?
Each formula was developed from different research populations and methodologies. The Epley, Brzycki, and Lander formulas all make slightly different mathematical assumptions about the relationship between weight and reps. The differences are usually small (within 5%) and all provide useful estimates for training purposes.