Which 1RM formula is the most accurate?

None is universally best — they were fitted to different lifter populations. Brzycki tends to read slightly lower and Epley slightly higher at moderate reps, while Lombardi rises most slowly. Averaging them, as this tool does, smooths out the individual biases. All three are most reliable at five reps or fewer.

Why do the estimates disagree at high reps?

Every formula is a curve fit to real lifting data, and the relationship between reps and percentage of max is only approximately linear at low reps. Past ~10 reps, endurance, fatigue resistance, and technique vary so much between people that the formulas spread apart and all become less trustworthy.

Should I actually test my one-rep max?

Most lifters don't need to. A true max attempt is fatiguing and carries injury risk without a spotter and solid technique. An estimate from a 3–5 rep set is accurate enough for programming. If you do test, warm up thoroughly, use a spotter or safety bars, and only attempt it occasionally.

How do I use the percentage-of-1RM table?

It converts your estimated max into training loads. Strength work lives around 85–95% for low reps; hypertrophy work sits near 70–80% for 6–12 reps; lighter technique or volume days use 70% and below. Adjust based on how the weight actually feels on the day.

Does this work for any lift?

The formulas are general and work for compound barbell lifts like squat, bench press, and deadlift, where most 1RM data was collected. They are less reliable for isolation movements, machines, and bodyweight exercises, where rep performance follows a different curve.

Reps or weight — which should I change to lift more?

For an accurate estimate, keep reps low and let the weight be honest: a heavy triple predicts your max better than a light set of twenty. The estimate is only as good as the set you put in — grind, partial, or assisted reps inflate it.

One-Rep Max Calculator

Three published strength formulas, plus a percentage-of-max training table.

Buğra SözeriHealth

Updated June 27, 2026 · Published June 27, 2026

Reviewed by Convertitive Health Desk

Medical disclaimer: This calculator is a screening reference, not a medical diagnosis. Consult a qualified healthcare professional before making decisions based on the result.

Your one-rep max (1RM) is the heaviest weight you can lift for a single clean repetition of an exercise. Testing it directly is fatiguing and — without a spotter and good technique — risky, so coaches usually estimate it from a submaximal set: a weight you lifted for several reps. The calculator below applies the three most-cited estimation formulas (Epley, Brzycki, and Lombardi), averages them, and turns that number into a percentage-of-max training table. The estimates diverge as reps climb and are most accurate for sets of roughly ten reps or fewer.

Weight lifted (kg)

Reps performed

Estimated one-rep max

115.5 kg

Average of the three formulas below.

Epley

116.7 kg

Brzycki

112.5 kg

Lombardi

117.5 kg

Training loads (% of estimated 1RM)

% of 1RM	Load (kg)	Typical use
95%	109.8	Heavy singles / peaking
90%	104	Strength, 2–4 reps
85%	98.21	Strength, 4–6 reps
80%	92.43	Hypertrophy, 6–8 reps
75%	86.66	Hypertrophy, 8–10 reps
70%	80.88	Volume / technique, 10–12 reps

Estimates only — most accurate for sets of ~10 reps or fewer. Not a substitute for a coached, supervised max attempt. Lift within your limits.

How to use

Enter a working set
Type the weight you lifted and the number of clean reps you completed. Choose kg or lb — the unit of your input is the unit of every result.
Read your estimated 1RM
The big number is the average of the Epley, Brzycki, and Lombardi estimates; the three are also shown individually so you can see how much they agree.
Program from the percentage table
Use the % of 1RM rows to pick training loads: ~85–95% for strength singles and triples, ~70–80% for hypertrophy sets of 6–12. Keep reps low (≤10) when the goal is an accurate max estimate.

Worked example: 100 kg for 5 reps

Lift 100 kg for 5 reps and the three formulas land close together — which is exactly why low-rep sets give the most trustworthy estimate.

Formula	Equation	Estimated 1RM
Epley	100 × (1 + 5/30)	116.7 kg
Brzycki	100 × 36 / (37 − 5)	112.5 kg
Lombardi	100 × 5^0.10	117.5 kg

Average ≈ 115.6 kg. Push the same lift to 15+ reps and the formulas fan out by 10 kg or more — the math, and your form, both degrade.

Frequently asked questions

Which 1RM formula is the most accurate?: None is universally best — they were fitted to different lifter populations. Brzycki tends to read slightly lower and Epley slightly higher at moderate reps, while Lombardi rises most slowly. Averaging them, as this tool does, smooths out the individual biases. All three are most reliable at five reps or fewer.
Why do the estimates disagree at high reps?: Every formula is a curve fit to real lifting data, and the relationship between reps and percentage of max is only approximately linear at low reps. Past ~10 reps, endurance, fatigue resistance, and technique vary so much between people that the formulas spread apart and all become less trustworthy.
Should I actually test my one-rep max?: Most lifters don't need to. A true max attempt is fatiguing and carries injury risk without a spotter and solid technique. An estimate from a 3–5 rep set is accurate enough for programming. If you do test, warm up thoroughly, use a spotter or safety bars, and only attempt it occasionally.
How do I use the percentage-of-1RM table?: It converts your estimated max into training loads. Strength work lives around 85–95% for low reps; hypertrophy work sits near 70–80% for 6–12 reps; lighter technique or volume days use 70% and below. Adjust based on how the weight actually feels on the day.
Does this work for any lift?: The formulas are general and work for compound barbell lifts like squat, bench press, and deadlift, where most 1RM data was collected. They are less reliable for isolation movements, machines, and bodyweight exercises, where rep performance follows a different curve.
Reps or weight — which should I change to lift more?: For an accurate estimate, keep reps low and let the weight be honest: a heavy triple predicts your max better than a light set of twenty. The estimate is only as good as the set you put in — grind, partial, or assisted reps inflate it.

About

The three formulas

Epley (1985): 1RM = weight × (1 + reps/30). Brzycki (1993): 1RM = weight × 36 / (37 − reps), undefined at 37+ reps. Lombardi (1989): 1RM = weight × reps^0.10. Each returns the lifted weight unchanged at a single rep, then diverges as reps increase — Epley and Brzycki roughly linearly, Lombardi as a gentle power curve.

Estimates, not guarantees

These equations describe population averages, not your individual strength curve. Two lifters with the same five-rep weight can have genuinely different true maxes depending on muscle-fiber make-up and fatigue resistance. Treat the output as a well-informed starting point for programming, and refine it against how loads actually feel in training.

Sources & references

Authoritative references behind the math, constants, and tables on this page. Verified by Buğra Sözeri on the dates shown and re-checked at every deploy.

Epley B. — Poundage Chart (Boyd Epley Workout, 1985) — Origin of the Epley formula, 1RM = weight × (1 + reps/30); an estimate most accurate at low rep counts(as of 2026-06-27)
Brzycki M. — Strength testing: predicting a one-rep max from reps-to-fatigue (JOPERD, 1993) — Source of the Brzycki formula, weight × 36 / (37 − reps); undefined at 37+ reps and intended for low-to-moderate reps(as of 2026-06-27)
Lombardi V.P. — Beginning Weight Training (Wm. C. Brown, 1989) — Source of the Lombardi formula, weight × reps^0.10; like the others, an estimate best applied to low-rep sets(as of 2026-06-27)