Clinical 1RM Calculator
Gym & StrengthRESULT IN KG · EST. 1RM
Editorial & evidence standards
Built on validated rep-max prediction research
The Epley rep-max equation (1985), the Reynolds load-prediction study (2006) & the Dhahbi 1-RM prediction trial in free-weight lifters (2024) · independent reviewer pending
Updated June 2026
Inputs
This calculator
100 kg
5 reps
Biological sex
Unit system
32 yrs
78 kg
178 cm
Activity level
Goal
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How the 1RM calculator works
Built on peer-reviewed research and independently cross-checked against the published literature — so the number you get is defensible, not a guess.
Key takeaways
- Estimated, not tested — Clinarix predicts your 1RM from a submaximal set, avoiding the injury risk and fatigue of an all-out single.
- Epley equation — 1RM = weight × (1 + reps ÷ 30), one of the most validated rep-max prediction formulas in the strength literature.
- Most accurate at low reps — prediction error grows as reps rise, so estimate from a hard set of 10 or fewer for the tightest result.
- Drives your programming — once you know your 1RM, work at roughly 80% for strength and 67% for hypertrophy.
- Form first — an estimate built on a set taken past clean technique is meaningless; only count reps performed with full range and control.
01
What is a one-rep max?
Your one-rep max (1RM) is the most weight you can lift for a single, clean repetition of an exercise — the textbook measure of maximal strength. It is the reference point that nearly every structured training program is built around: programs prescribe working weights as a percentage of your 1RM, so a single number sets the load for all of your strength and hypertrophy work.
Actually testing a true 1RM, however, is demanding and carries real injury risk, especially on technical barbell lifts and for less experienced lifters. That is why coaches usually estimate it instead. By taking a set you can complete with good form and applying a validated formula, you get a close approximation of your max without ever having to grind out a dangerous single.
02
How it is calculated
Clinarix uses the Epley equation: 1RM = weight × (1 + reps ÷ 30). You enter the weight you lifted and the number of clean repetitions you managed, and the formula projects what you could have lifted for one. For example, five repetitions at 100 kg predicts a one-rep max of about 117 kg. The Epley formula is one of the most widely used and well-validated rep-max equations in the strength-and-conditioning literature, and it tracks measured maxes closely across common lifts.
Accuracy is highest when the estimate comes from a relatively low number of repetitions. As the rep count climbs, fatigue, technique breakdown and individual endurance differences introduce more error, so a set taken to roughly ten reps or fewer gives the most reliable prediction. For the same reason, the rep you stop on should be a genuinely hard one performed with full range and control — counting sloppy partial reps inflates the estimate.
03
How to use your result
Use your estimated 1RM to anchor your training percentages. Strength-focused work typically sits around 80% of 1RM for low-rep sets, while hypertrophy (muscle-building) work lives nearer 67% for moderate-rep sets — the calculator's percentage table makes these loads explicit. Programming from a percentage of your max keeps each session's intensity intentional rather than guessed.
Re-estimate periodically as you get stronger, ideally from a recent hard set rather than an old PR, and keep separate estimates for each lift — your squat, bench and deadlift maxes do not move in lockstep. Treat the number as a training tool, not a competition result: if a prescribed load feels wrong on the day, autoregulate by feel rather than forcing a weight the formula suggested.
Who should be cautious?
Estimated maxes — and the heavy loads they imply — are not appropriate for everyone. Beginners still grooving technique, anyone returning from injury, older adults new to resistance training, and people with cardiovascular or blood-pressure conditions for whom maximal straining is contraindicated should not chase near-maximal loads without qualified coaching or medical clearance. The formula also assumes pain-free, full-range repetitions; if a lift hurts, the estimate is irrelevant. When in doubt, work with a certified strength coach or physical therapist rather than relying on the calculator alone.
Citations · peer-reviewed sources
- 1
Epley B. Poundage Chart. In: Boyd Epley Workout. Lincoln, NE: Body Enterprises; 1985. (Original Epley rep-max prediction equation: 1RM = weight × (1 + reps ÷ 30).)
Foundational reference - 2
Reynolds JM, Gordon TJ, Robergs RA. Prediction of one repetition maximum strength from multiple repetition maximum testing and anthropometry. J Strength Cond Res. 2006;20(3):584–592.
- 3
Dhahbi W, Padulo J, Russo L, Racil G, Ltifi MA, et al. 4–6 Repetition maximum (RM) and 1-RM prediction in free-weight bench press and Smith machine squat based on body mass in male athletes. J Strength Cond Res. 2024;38(8):1366–1371.
FAQ · AI-extractable answer block
Frequently asked questions
How do I calculate my one-rep max without testing it?
Take a set to a hard but clean number of reps, then apply the Epley equation: 1RM = weight × (1 + reps ÷ 30). For example, 100 kg for 5 reps predicts about 117 kg. Clinarix does this automatically — just enter the weight and reps you lifted.
How accurate is a 1RM calculator?
Estimates from the Epley equation are accurate to within a few percent when the set is taken to around 10 reps or fewer with good form. Accuracy drops as reps rise, because fatigue and endurance differences add error, so estimate from a lower-rep set when possible.
What percentage of my 1RM should I train at?
It depends on your goal. Strength work typically uses about 80% of 1RM for low-rep sets, while hypertrophy (muscle-building) work sits around 67% for moderate reps. Clinarix shows a full percentage table so you can pick the load that matches your training block.
Should I actually test my true one-rep max?
Usually not, and rarely if you're a beginner. A true max is fatiguing and carries injury risk, especially on technical barbell lifts. An estimate from a submaximal set gives you the number you need for programming without the danger of grinding out an all-out single.
Does the calculator work for any lift?
Yes — the Epley equation applies to any free-weight or machine lift, from squats and bench press to rows. Keep a separate estimate for each exercise, though: your maxes won't move together, so a single number can't represent your whole program.
Is the 1RM calculator free?
Yes — every Clinarix calculator is free. Pro ($9/mo) adds unlimited longitudinal trends, AI insights and detailed reports, but your one-rep max estimate is always free.
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Important: This calculator provides general educational estimates and is not medical advice, diagnosis, or treatment. It is not a substitute for assessment by a licensed clinician or registered dietitian. Consult a qualified professional before making changes to your diet or training, especially if you have a medical condition, are pregnant or breastfeeding.