1RM via Epley, Brzycki, Lander, Lombardi, Mayhew, O'Conner and Wathan formulas.
Updated
Set details
Best accuracy at 2–10 reps. Above 10 reps the prediction error grows.
Estimated 1RM
Average of seven formulas
115.5 kg
Epley (1985)
116.7 kg
Brzycki (1993)
112.5 kg
Lander (1985)
113.7 kg
Lombardi (1989)
117.5 kg
Mayhew (1992)
119.0 kg
O'Conner (1989)
112.5 kg
Wathan (1994)
116.6 kg
% of 1RM
Working weight
Approx. reps
100%
115.5 kg
1
95%
109.7 kg
2
93%
107.4 kg
3
90%
103.9 kg
4
87%
100.5 kg
5
85%
98.2 kg
6
83%
95.9 kg
7
80%
92.4 kg
8
77%
88.9 kg
9
75%
86.6 kg
10
70%
80.8 kg
12
67%
77.4 kg
15
Quick start
How to estimate your 1RM
Enter the weight and rep count of a recent set to failure. The calculator predicts your 1RM via seven published formulas plus a percent-of-1RM working-weight table.
Step 1
Pick units
Switch between kilograms and pounds.
Step 2
Enter the set
Type the weight you lifted and the rep count to (or near) failure. Best accuracy at 2–10 reps.
Step 3
Read the band
Average of seven 1RM estimates plus a working-weight table at 67–100% of 1RM for percentage-based programming.
In-depth guide
One rep max — seven formulas, one strength curve
Your one-rep max (1RM) is the heaviest weight you can move for a single clean rep on a given lift. Seven published formulas turn a submaximal set (e.g. 100 kg × 5) into a 1RM estimate. They agree within ~5 kg at low reps; this tool shows all seven plus the average so you can read the band rather than commit to one curve.
The seven formulas
w = weight lifted, r = reps to (or near) failure. Result in the same unit as input.
All seven formulas were fit on data with rep counts in the 1–10 range. Beyond about 10 reps, technique fatigue, breathing recovery and neural fatigue start to confound the simple "weight × reps" pattern. At 15+ reps expect ±10–15% error — treat the result as a rough guide.
The most accurate single test is a clean 3RM or 5RM, with a spotter, after a thorough warm-up. Hard 1RM testing has injury risk and the number is noisy unless you've tested the lift many times before.
The percent-of-1RM table
Once you have an estimated 1RM, the rep table converts it into working weights for percentage-based programming. Common patterns:
5×5 at 85% (six reps in reserve) — classic strength block.
3×8 at 75% — hypertrophy work.
5×3 at 90% — peaking / max strength.
3×12 at 70% — accessory volume.
Most gains come from sub-90% work over weeks and months. Don't max-test often — it's a measurement, not a stimulus.
Form matters
Predicted 1RM assumes the rep was clean. Grindy reps with form breakdown have "further to go" on the strength curve than they look — the bar moved the same distance but compensations covered for fatigued tissue. If form fell apart on rep 8 of 10, count seven; if rep 5 of 5 was a grinder, the prediction is at the upper bound of reality.
For Olympic lifts (snatch, clean & jerk), the prediction is far less reliable because technique failure precedes muscular failure. These formulas were derived from squat / bench / deadlift / press data.
Frequently asked questions
Is my data uploaded anywhere?
No. The 1RM formulas run entirely in your browser as you type. Nothing is sent to a server, stored, or logged.
Why seven formulas?
Each was derived from regression on a different lifter population. Epley (1985), Brzycki (1993), Lander (1985), Lombardi (1989), Mayhew (1992), O'Conner (1989) and Wathan (1994) typically agree within 5 kg at 1–8 reps. Showing all seven plus the average gives a band — useful for picking working weights without overcommitting to one curve.
Which formula is most accurate?
It depends on the lift and the lifter. Brzycki and Epley are the two most commonly used in coaching. Mayhew and Wathan use exponential terms that fit better at higher reps. Lombardi tends to underpredict at low reps. Use the average of seven as a robust estimate, and recalibrate against an actual gym test once you've trained the move.
How many reps should I use?
Best accuracy at 2–10 reps to failure. Above 10 the prediction error grows (technique fatigue, breathing recovery, neural fatigue all confound the pattern). Above 15 reps, expect ±10–15% error — treat the result as a rough guide.
Does this work for any lift?
Best for the big compound lifts (squat, bench, deadlift, overhead press, row) where the rep speed/effort relationship is well-studied. Less reliable for isolation lifts (curls, lateral raises) and Olympic lifts where technique failure precedes muscular failure.
How should I use the percent-of-1RM table?
It's the foundation of percentage-based programming. 5×5 at 85% of 1RM is a classic strength block; 3×8 at 75% sits in the hypertrophy band. Avoid 'going for max' often — most strength gains come from sub-90% work.
Should I actually test my 1RM?
Once you've trained a lift for 6+ months and know your technique under load, a true 1RM test (well warmed up, with a spotter) is useful for calibration. Don't max-test untrained or untechnical lifts — the injury risk is real and the number is noise.
What if my reps are with poor form?
Predicted 1RM assumes the rep was clean. Grindy reps with form breakdown have 'further to go' on the strength curve than they appear; the formulas will overestimate. If form fell apart on rep 8 of 10, count 7.
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