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What is One Rep Max Calculator?

Free one rep max calculator. Enter weight lifted and reps to get 1RM estimates from 6 formulas side-by-side (Brzycki, Epley, Lander, Lombardi, Mayhew, O'Conner) plus a full percentage training table. No signup.

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Free One Rep Max Calculator

Estimate your one-rep max from any working set. Enter the weight and reps performed, and see 1RM predictions from all 6 major formulas side-by-side so you can compare the range and choose the most relevant estimate for your rep range. Includes a full percentage table (50–100% of 1RM) for training program design.

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Estimated 1RM — average of 6 formulas

260 lb

Brzycki

253 lb

Most accurate for 1–10 reps

Epley

263 lb

Common in fitness software, 1–12 reps

Lander

256 lb

Conservative estimate, good for 1–10 reps

Lombardi

264 lb

Tends high for large rep counts

Mayhew

268 lb

Validated for athletic populations

O'Conner

253 lb

Simple linear approximation

Training percentage table

Based on average 1RM estimate of 260 lb

100%260 lb~1 reps
97%252 lb~1 reps
95%247 lb~2–3 reps
93%242 lb~2–3 reps
90%234 lb~3–4 reps
87%226 lb~4–5 reps
85%221 lb~4–5 reps
80%208 lb~6–8 reps
75%195 lb~8–12 reps
70%182 lb~8–12 reps
65%169 lb~12–16 reps
60%156 lb~12–16 reps
55%143 lb~15–20+ reps
50%130 lb~15–20+ reps

🏋️ Ready to put your 1RM to work?

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Frequently Asked Questions

Your one-rep max is the maximum weight you can lift for exactly one complete repetition with proper form. It is the universal standard for measuring absolute strength in powerlifting and strength training. Direct 1RM testing is accurate but carries injury risk, especially for beginners — calculated estimates from submaximal sets provide a safer alternative.
Accuracy varies by rep range. Brzycki is most accurate for sets of 1–10 reps and is widely used in powerlifting. Epley is reliable for sets of 1–12 reps and is the most common formula used in fitness software. Lander and Mayhew perform well in the 1–10 rep range. All formulas become less accurate above 10–12 reps because fatigue factors increase prediction error. Use the Brzycki or Epley estimate as your primary reference.
The percentage table shows what weight corresponds to each percentage of your estimated 1RM. Common training zones: 90–100% = maximal strength (1–3 reps), 80–90% = strength/power (3–5 reps), 70–80% = strength/hypertrophy (5–8 reps), 60–70% = hypertrophy (8–12 reps), 50–60% = muscular endurance or speed work (12–20+ reps). Most evidence-based strength programs (5/3/1, GZCLP, Texas Method) prescribe work sets as a percentage of your training max.
Most coaches recommend using 90% of your tested or estimated 1RM as your "training max" — the number you base programming percentages on. This buffer accounts for day-to-day variation in performance (sleep, stress, nutrition) and prevents you from missing prescribed lifts when you have a subpar training day. The 5/3/1 program by Jim Wendler popularized this approach.
Testing a true 1RM is safe for trained individuals who have mastered the movement pattern and have a competent spotter (for bench press and squat). For beginners and for exercises where a failed rep cannot be safely bailed (many machine exercises), estimating from a 3–5 rep set is safer and produces reliable estimates. Never attempt a true 1RM test without a warm-up, spotter, and familiarity with the exercise.

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Using Your 1RM for Programming

Your estimated 1RM is most useful as a reference for calculating training weights across a periodized program. Most evidence-based programs prescribe work sets as a percentage of your 1RM or training max (typically 90% of 1RM). The percentage table in the calculator above gives you every weight increment from 50–100% instantly.

Which Formula to Trust

For sets of 1–5 reps, Brzycki and Epley produce nearly identical results and are both well-validated. Above 10 reps, prediction error increases significantly for all formulas — this is why most coaches recommend basing your 1RM estimate on a set of 3–5 reps rather than 10–15. When multiple formulas are clustered closely together, that cluster represents the most likely true value.

Training Max vs. True 1RM

Jim Wendler's 5/3/1 program popularized using 90% of your 1RM as a "training max" — the number you base all percentages on. This buffer prevents missed lifts on hard days and ensures you accumulate quality volume rather than grinding at true max effort. For most intermediate lifters, a training max of 85–90% of estimated 1RM is optimal.

Pair With Structured Programming

Once you know your 1RM, the next step is a program that puts it to use. Try RowGress workouts for structured strength programming, grab today's WOD, or explore all free fitness calculators for macro and calorie planning to fuel your training.