One-Rep Max (1RM) Calculator

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Estimated 1-Rep Max by Formula

式	Estimated 1RM
Epley	-
Brzycki	-
Lombardi	-
O'Conner	-
Wathan	-
平均	-

Percentage of 1RM Rep Chart

% of 1RM	重さ	Est. Reps
100%	-	1
95%	-	2
90%	-	4
85%	-	6
80%	-	8
75%	-	10
70%	-	12
65%	-	15
60%	-	17
55%	-	20
50%	-	25

Warm-up Set Calculator

Suggested warm-up progression based on your estimated 1RM. Rest 1-3 minutes between sets.

セット	% of 1RM	重さ	Reps
1 (Bar warm-up)	30%	-	8-10
2	50%	-	5
3	70%	-	3
4	85%	-	2
5 (Final primer)	90%	-	1

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One-Rep Max (1RM) Calculator

Estimate your one-rep max from any working set without ever loading a maximal attempt. Plug in the weight you lifted and the number of clean reps to failure, and the calculator returns five validated 1RM estimates (Epley, Brzycki, Lombardi, O’Conner, Wathan), the average across formulas, a percentage-of-1RM rep chart, and a five-set warm-up progression. Toggle between kilograms and pounds to match how your gym is set up.

使用方法

Pick your unit — kilograms or pounds.
そこで登場するのが weight you actually lifted (bar plus plates).
そこで登場するのが reps you completed to failure. Stay between 1 and 15 — beyond that the formulas drift fast.
Read off the estimated 1RM from each formula and use the average as your working number.
Use the percentage chart to plan your next training block, or the warm-up table to build into a heavy single.

機能

Five formulas side by side — Epley, Brzycki, Lombardi, O’Conner, and Wathan, plus a cross-formula average so you can spot outliers.
Percentage-of-1RM rep chart — weights for 50% through 100% of your estimated max with the typical rep target at each load.
Warm-up calculator — a five-set ramp at 30 / 50 / 70 / 85 / 90 percent so you arrive primed without burning out.
kg / lb toggle — outputs round to plate-friendly increments (1 kg or 2.5 lb) for both units.
Live results — every number updates as you type. No submit button, no page reload.

 よくある質問

Why do different 1RM formulas give different numbers?

Each formula was derived from a different population and lift type. Epley and Brzycki were calibrated mostly on the bench press in the 1-10 rep range; Wathan used a broader sample including powerlifters. Lombardi is a power curve that handles higher reps better. The average across formulas usually lands closer to a true tested 1RM than any single estimate.
How accurate are 1RM estimates?

Within 1-5 reps the best formulas typically fall within 5% of a true tested max. Accuracy degrades as reps increase because fatigue, technique breakdown, and rep tempo all start to matter more than raw load. Above 12-15 reps the prediction is more about muscular endurance than maximal strength, which is why most 1RM tools cap their input there.
Should I actually test my 1RM in the gym?

For most lifters, no. True 1RM testing is high-risk, requires a long taper, and gives one data point. Submaximal testing — for example a heavy set of 3-5 reps — is safer, repeatable, and feeds straight into estimation formulas. Competitive powerlifters and weightlifters do test maxes, but typically only on meet day after a planned peaking block.
What is the percentage-of-1RM method used for?

It is the backbone of percentage-based programming. Once you know your estimated 1RM, you can target specific training adaptations by load: roughly 85-100% for maximal strength, 70-85% for hypertrophy and strength endurance, and 50-70% for power, technique, and warm-up work. Programs like Wendler 5/3/1 and the Texas Method are built on these percentage brackets.
Why warm up with five sets instead of jumping straight to the working weight?

Progressive warm-up sets do three things: raise tissue temperature and synovial fluid for joint readiness, rehearse the motor pattern under increasing load, and recruit the high-threshold motor units needed for heavy work. Skipping the ramp leaves the nervous system under-primed, which usually shows up as a sluggish or technically poor first working set.