One Rep Max Calculator
Estimate your one-rep max from any weight/reps combo using 6 strength-training formulas, plus a full training percentage chart. Free, no sign-up.
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Your Lift
Formulas to Compare
Epley and Brzycki are the two most widely used formulas in strength coaching. The rest are shown for comparison.
Estimated One-Rep Max
155 lbs
Range across selected formulas: 152.5 lbs – 157.5 lbs
By Formula
Training Percentage Chart
| % of 1RM | Weight | Typical Reps |
|---|---|---|
| 100% | 155 lbs | 1 |
| 95% | 147.5 lbs | 2 |
| 90% | 140 lbs | 4 |
| 85% | 132.5 lbs | 6 |
| 80% | 125 lbs | 8 |
| 75% | 115 lbs | 10 |
| 70% | 107.5 lbs | 12 |
| 65% | 100 lbs | 15 |
| 60% | 92.5 lbs | 18–20 |
| 50% | 77.5 lbs | 20+ |
"Typical reps" are standard strength-coaching estimates, not calculated from your specific lift.
These formulas estimate a theoretical max from a submaximal set — they don't replace an actual tested 1RM. Never attempt a true one-rep max without a qualified spotter, proper warm-up, and good form. This tool is for training reference only, not medical or professional coaching advice.
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Buy me a coffeeFree One-Rep Max Calculator — Epley, Brzycki & 4 More Formulas
You don't need to grind out a true max-effort single to know roughly where your one-rep max sits. Enter any weight and rep combo you've actually completed — a set of 5 at 135 lbs, for example — and this calculator estimates your 1RM using six established strength-training formulas, then builds a full training percentage chart from the result. Everything runs instantly in your browser with plain JavaScript, no sign-up required.
Planning your training week around these numbers? Browse the rest of the health & fitness calculators for more tools to round out your program.
Why Do the Formulas Give Different Numbers?
Every 1RM formula is a curve fitted to real lifting data, and no two research teams fit that curve the same way — so estimates naturally diverge, especially as rep count goes up. Epley and Brzycki are the most widely used in strength coaching and tend to agree closely in the 1–10 rep range. Lombardi and O'Conner are slightly more conservative for higher-rep sets, while Wathan and Mayhew were both derived from athletic-population studies and can run a bit higher. Comparing several formulas at once — rather than trusting a single number — gives you a realistic range instead of false precision.
📉 Accuracy drops with higher reps
All formulas are most accurate for sets of 1–10 reps. Above ~12 reps, fatigue and technique breakdown make every formula less reliable.
📊 Averages beat single formulas
Averaging several formulas smooths out each one's individual bias, giving a more dependable estimate than picking just one.
How to Use Your 1RM for Programming
Program off percentages, not raw numbers
Most strength programs prescribe work as a % of your 1RM (e.g. "5x5 at 75%"). Use the training percentage chart above to convert that straight into a loadable weight.
Re-test every 4–8 weeks
Your estimated 1RM changes as you get stronger. Re-run the calculator with a fresh, recent set rather than relying on numbers from months ago.
Use a rep range you can complete with good form
Estimates from a clean set of 3–8 reps are generally more reliable than a grindy set taken close to failure.
Treat it as an estimate, not a target to hit cold
Don't load up the calculated 1RM and attempt it without a proper warm-up ramp and a spotter — these formulas predict a theoretical max, not a guaranteed safe lift.
Track it per lift
Squat, bench, deadlift, and overhead press all respond differently to training — run the calculator separately for each rather than assuming one ratio applies to all.
Frequently Asked Questions
How accurate is an estimated 1RM compared to a tested max?
It's a solid estimate, typically within a few percent of a real tested max for sets of 10 reps or fewer performed with good form — but it's still an estimate, not a substitute for an actual max-effort test under safe conditions.
Which formula should I trust most?
Epley and Brzycki are the two most widely used in strength coaching and are a reasonable default. This calculator lets you compare several at once and shows the average, which tends to be more reliable than any single formula.
Why does the estimate change so much at higher rep counts?
All 1RM formulas are curve fits based on lower-rep data (typically 1–10 reps). Fatigue and form breakdown at higher rep counts make every formula's prediction less reliable the further out you go.
What is the training percentage chart for?
It converts your estimated 1RM into the actual weight to load for common training percentages (e.g. 80% for an 8-rep hypertrophy set), which is how most structured strength programs prescribe working weight.
Is it safe to attempt the calculated weight for a single rep?
Not without preparation. Always work up to any heavy single with a proper warm-up ramp, good technique, and a spotter or safety setup — a calculated 1RM is a planning estimate, not a lift you should attempt cold.
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