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.
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About One Rep Max Calculator
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.
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