Estimate your one-rep max from a weight and rep count using Epley, Brzycki, and Lombardi, in your browser. A general estimate, not medical advice.
One Rep Max Calculator Online
Estimate your one-rep max from a weight and rep count using Epley, Brzycki, and Lombardi, in your browser. A general estimate, not medical advice.
The One Rep Max Calculator runs entirely in your browser and the weight and reps you enter never leave your device. Results are a general estimate using standard strength-training formulas, not medical advice.
One Rep Max Calculator estimates the heaviest weight you could lift for a single rep from a weight and rep count you already completed. It runs three standard strength formulas — Epley, Brzycki, and Lombardi — side by side, averages them, and builds a percent-of-1RM table so you can plan warm-up sets and training percentages straight from the result. Enter the weight lifted and how many reps you completed, switch between kg and lb, and copy a plain-text summary for your training log. It is useful for powerlifters, bodybuilders, and coaches programming a bench press, squat, or deadlift cycle without doing an all-out max attempt. This is a general estimate using standard strength-training formulas, not medical advice — lift within your ability and consult a coach or medical professional before attempting a new maximum. Everything runs locally in your browser.
Features
Estimates 1RM using the Epley, Brzycki, and Lombardi formulas side by side
Shows an averaged estimate across all three formulas
Builds a percent-of-1RM training table from 50% to 100%
Switches between kilograms and pounds with one click
Copy button for a plain-text summary of the weight, reps, and estimates
Clear error message when the weight or rep count is missing or invalid
Notes clearly that results are general estimates, not medical advice
Runs entirely in your browser with no lift data sent anywhere
How to use the One Rep Max Calculator
Enter the weight you lifted and choose kg or lb
Enter the number of reps you completed with that weight
Read the Epley, Brzycki, Lombardi, and average 1RM estimates
Scroll the percent-of-1RM table to plan warm-up and training loads
Copy the summary to save it in your training log
Example
Input
100 kg × 5 reps
Output
1RM: ~117 kg (Epley)
Common errors & troubleshooting
The rep count was entered as a decimal like 5.5 and the calculator flags it as invalid. — The One Rep Max Calculator needs a whole number of completed reps — round down to the last fully completed rep.
A very high rep count (like 30+) makes the estimate feel unrealistic. — 1RM formulas are most accurate for sets of 1–10 reps. For higher-rep sets, treat the estimate as a rough guide rather than a precise number.
The Epley and Brzycki estimates differ by a noticeable amount. — This is normal — each formula weights reps slightly differently. Use the average, or whichever formula you have found tracks your actual max most closely.
The unit toggle was left on lb after typing a kilogram figure. — Switch the kg / lb toggle to match the unit you actually lifted in before reading the result.
Frequently asked questions
What formulas does the One Rep Max Calculator use?
It calculates Epley (weight × (1 + reps/30)), Brzycki (weight × 36 / (37 − reps)), and Lombardi (weight × reps^0.10), then averages all three for a single estimate.
How accurate is the One Rep Max Calculator?
It is a general estimate using standard strength-training formulas, most accurate for sets of roughly 1–10 reps. It is not medical advice and can differ from your true one-rep max.
What is the percent-of-1RM table in the One Rep Max Calculator for?
It converts your averaged 1RM estimate into a range of training percentages (50%–100%), which is handy for programming warm-up sets and working weights for a lifting cycle.
Can the One Rep Max Calculator use pounds instead of kilograms?
Yes. Use the kg / lb toggle next to the weight field — the formulas are unit-agnostic, so the result is shown in whichever unit you select.
Does the One Rep Max Calculator upload my lift data anywhere?
No. The One Rep Max Calculator runs entirely in your browser. The weight and reps you enter never leave your device.
Should I trust the One Rep Max Calculator over an actual max attempt?
No. It gives a general estimate only, not medical advice. Use it to plan training percentages, but always work up to a true max carefully and with proper spotting or supervision.