How to estimate your one-rep max without testing it
How a set you have already lifted turns into an estimated max, how far to trust it, and how to use it to pick loads.
Last reviewed October 15, 2026
To estimate your one-rep max, lift a weight for as many good reps as you can, up to 10, and put the weight and reps into a prediction equation.[1] Fewer reps give a better estimate, and any equation can miss by a margin.[1, 2] Dalia's coach uses the Epley formula: weight × (1 + reps ÷ 30).
Key takeaways
- Your one-rep max (1RM) is the most weight you can lift once, and it can be estimated from a set taken to failure.[1]
- In one study, a 5-rep max predicted 1RM better than 10- or 20-rep maxes, and the authors advise using no more than 10 reps in linear equations.[1]
- In 220 men, equations like these over- or under-predicted bench press 1RM, and averaging two equations may reduce the error.[2]
- Dalia's coach uses the Epley formula to estimate 1RM from a logged set.
What a one-rep max is
- One-rep max (1RM)
- The heaviest load you can lift for a single repetition. Researchers write it as 1RM and test it against sets of 5, 10 or 20 reps to failure.[1]
Researchers have found that 1RM can be estimated accurately from a set of several reps to failure instead.[1]
The formulas
Dalia's coach uses the Epley formula: weight × (1 + reps ÷ 30), rounded to one decimal. A single rep is its own max. It makes no estimate from more than 12 reps.
The calculator also shows the Brzycki equation, weight × 36 ÷ (37 − reps), for comparison. In a study of 220 men, the Brzycki equation was the most accurate of six for people who did 10 reps or fewer.[2]
Worked example
An estimated max from one set
Take a lifter who bench presses 185 lb for 5 good reps and could not do a sixth.
Epley
185 × (1 + 5 ÷ 30)
215.8 lb
Brzycki, for comparison
185 × 36 ÷ (37 − 5)
208.1 lb
Estimated one-rep max
about 216 lb (Epley)
Using the estimate to pick loads
Run Epley backwards and you get the load you could expect to lift for a given number of reps. For the lifter above:
| Reps | Load | Share of max |
|---|---|---|
| 1 | 216 lb | 100% |
| 3 | 196 lb | 91% |
| 5 | 185 lb | 86% |
| 8 | 170 lb | 79% |
| 10 | 162 lb | 75% |
| 12 | 154 lb | 71% |
The one-rep max calculator builds this table from any set you enter.
How accurate the estimate is
In 70 adults, a 5-rep max predicted 1RM better than a 10- or 20-rep max.[1] The load did not fall in a straight line as reps went up, and the authors say no more than 10 reps should be used in linear equations.[1]
In 220 men across seven groups, from untrained students to football players, all six equations tested were strongly linked to the real max.[2] Even so, among men who did 10 reps or fewer, three equations over-predicted and two under-predicted.[2] The authors suggest caution and say averaging two equations may reduce the error.[2]
So treat the number as a starting point. In the study above, a set of 5 reps to failure gave the best prediction.[1] Your next sessions will show whether the loads it suggests are right. Lifting days also count toward the activity level you pick when you estimate your daily burn.
When to talk to a clinician
References & further reading
- 1.Prediction of one repetition maximum strength from multiple repetition maximum testing and anthropometry, Journal of Strength and Conditioning Research (Reynolds et al.), 2006
- 2.Muscular endurance repetitions to predict bench press strength in men of different training levels, Journal of Sports Medicine and Physical Fitness (Mayhew et al.), 1995
- 3.Resistance exercise training in individuals with and without cardiovascular disease: 2023 update, Circulation (Paluch et al., American Heart Association), 2024
- 4.Resistance exercise in individuals with and without cardiovascular disease: 2007 update, Circulation (Williams et al., American Heart Association), 2007
Eashan Vagish
Founder, Dalia Health
Eashan Vagish is the founder of Dalia Health, where he works on making heart and metabolic health easier to understand and track. He writes these guides to answer the health questions people actually ask, in plain language, with links to the research behind every claim.
Medical disclaimer: This article is for general educational purposes only and is not medical advice. It is not a substitute for diagnosis or treatment from a qualified healthcare professional. Always talk to your doctor about your individual health, and seek immediate care for any urgent symptoms.
How we write, source and correct these guides: our editorial policy. Spot an error? Email info@daliahealth.com.
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