What is my one-rep max?

People type this into search every day: one rep max calculator.

The usual answer is “add a plate and try.” A one-repetition maximum is the load you can lift once with the same technique you used on the set. Testing that load is a skill, and it is a stress. Most of the time you want an estimate from a set you already finished.

This page is a labeled example. It is not a training program, and it is not medical advice.

Two formulas, then the midpoint

The one-rep max estimate calculator averages two published equations:

Epley: weight × (1 + reps ÷ 30)

Brzycki: weight × 36 ÷ (37 − reps)

At 1 repetition both formulas return the weight you typed. From 2 through 12 they diverge, and the tool prints the average. It also prints 90% of the lower formula as a conservative reference.

The assumptions are blunt. The set used consistent technique and ended close to technical failure. The estimate is most useful for 2 to 10 repetitions and varies by exercise and person.

Matt Brzycki’s 1993 JOPERD article, Strength Testing—Predicting a One-Rep Max from Reps-to-Fatigue, is the source of the second formula. He wrote it because a true 1-RM attempt loads muscles, bones, and connective tissue, and it also pushes blood pressure. The article treats a submaximal set as the safer field test. A Princeton copy of that paper is on his scholar page.

The first formula is the Epley equation the calculator prints: add about 3.33% of the load for every extra repetition. That 3.33% is 1 ÷ 30. The percentage increase post is the same (new − old) ÷ old arithmetic if you want the percent written out.

Reynolds, Gordon, and Robergs, in the 2006 Journal of Strength and Conditioning Research paper, compared multiple-repetition tests with measured 1-RM on chest press and leg press. Their conclusion for linear equations is the line I care about: use no more than 10 repetitions. A 5-RM test predicted 1-RM more closely than 10-RM or 20-RM in that sample. That paper is not this site’s formula. It is the reason the calculator caps the input at 12 and calls 2 to 10 the useful window.

The published 80 kg × 5 example

Here are the calculator defaults:

• weight lifted: 80 kg
• completed repetitions: 5

Epley: 80 × (1 + 5 ÷ 30) = 80 × 7 ÷ 6 = 93.333… kg

Brzycki: 80 × 36 ÷ (37 − 5) = 2880 ÷ 32 = 90 kg

Average: (93.333… + 90) ÷ 2 = 91.667 kg

Conservative: min(93.333…, 90) × 0.9 = 81 kg

The site’s US profile prints kilograms as pounds. 80 × 2.204622622 = 176.4 lb on the input. The card prints the average as 202.1 lb, Epley as 205.8 lb, Brzycki as 198.4 lb, and the conservative line as 178.6 lb.

The average sits 3.7 lb above Brzycki and 3.7 lb below Epley. The spread is 205.8 − 198.4 = 7.4 lb. That gap is disagreement between two linear models, not an error bar for your lift.

Do not treat 202.1 lb as a load to attempt. The calculator note says not to attempt a maximal lift without suitable experience, technique, equipment, and supervision.

The same 80 kg, more repetitions

Keep 80 kg. Change only the completed reps. The US card prints pounds.

• 1 rep: 176.4 lb. Both formulas return 80 kg.
• 3 reps: average 190.4 lb. Epley 194 lb. Brzycki 186.7 lb.
• 5 reps: average 202.1 lb.
• 8 reps: average 221.2 lb. Epley 223.4 lb. Brzycki 218.9 lb.
• 10 reps: average 235.2 lb. Both formulas print 235.2 lb.
• 12 reps: average 250.4 lb. Epley 246.9 lb. Brzycki 254 lb.

At 10 reps the algebra agrees. Epley: 80 × (1 + 10 ÷ 30) = 80 × 4 ÷ 3 = 106.667 kg. Brzycki: 80 × 36 ÷ 27 = 106.667 kg. 80 ÷ 106.667 = 75%. Brzycki’s article uses that same 10-rep shortcut: divide the 10-rep load by 0.75. 80 ÷ 0.75 = 106.667 kg, which the US card shows as 235.2 lb.

Past 10 reps the models part again, and Brzycki’s article already treated that zone as anaerobic endurance more than a max test. Reynolds and colleagues said the same thing with different equipment: do not feed a linear equation a 20-rep set and expect a tight 1-RM. I would type 5, not 12, when I have a choice.

A heavier 5-rep set scales the same percentages. 100 kg × 5:

Epley: 116.667 kg (257.2 lb)

Brzycki: 112.5 kg (248 lb)

Average: 114.583 kg (252.6 lb)

Conservative: 101.25 kg (223.2 lb)

A lighter 8-rep set, 60 kg:

Average: 75.241 kg (165.9 lb)

Epley 167.6 lb. Brzycki 164.2 lb. Conservative 147.8 lb.

The conservative line is 90% of the lower formula

On the default 5-rep set the lower formula is Brzycki at 90 kg. 90 × 0.9 = 81 kg, printed as 178.6 lb.

That 178.6 lb is 178.6 ÷ 202.1 = 88.4% of the average estimate, and 178.6 ÷ 176.4 = 101.2% of the weight already on the bar. It is a reference, not a prescription. The tool will not decide whether you should lift it.

CDC’s what counts as adult activity page is a health guideline, not a 1-RM test. Adults need muscle-strengthening work on 2 or more days a week. The same page says to work to the point where another repetition is hard, and it names 8 to 12 repetitions as one set. The adult activity overview repeats the 2-day line next to 150 minutes of moderate aerobic activity.

8 to 12 reps is the CDC set for health. It is also the noisy end of a linear 1-RM equation. Use the estimate on a 3-rep or 5-rep set if you want the number. Use 8 to 12 if you are following the guideline and you do not need a max.

Session volume is a different calculator

The estimate is one lift. The workout volume calculator adds the session:

sets × repetitions × load × exercises

Defaults: 5 sets, 8 reps, 60 kg, 3 equivalent exercises.

Volume: 5 × 8 × 60 × 3 = 7,200 kg, printed as 15,873 lb

Total repetitions: 5 × 8 × 3 = 120

Volume per exercise: 2,400 kg, printed as 5,291 lb

Every set uses the same reps and load. The tool does not measure technique, safety, or recovery. 60 kg is 60 ÷ 91.667 = 65.5% of the default average estimate. That percentage is arithmetic on two labeled examples. It is not a program.

Four sets instead of five, same 8 × 60 × 3: volume 5,760 kg, printed as 12,699 lb. Total reps 96.

I am not going to turn 202.1 lb into a weekly plan. The volume tool is there so you can compare two sessions that already happened.

Open the one-rep max estimate calculator with a set of 2 to 10 reps you actually completed. Read both formulas and the conservative line. Use the workout volume calculator for the session total, not for a max attempt.