One rep max calculator

What the One Rep Max Calculator Does

This is the home of the One Rep Max calculator, plus everything around it: a plain-English explanation of One Rep Max, input-by-input guidance, the formula revealed, and a step-by-step worked example with real numbers. Skip the risky true max test — a one rep max calculator estimates your 1RM from a safer submaximal set using the proven Epley formula.

You may also need our Marathon Pace calculator, Calories Burned Walking calculator, BAC (Blood Alcohol) calculator — they cover the neighbouring calculations people usually run alongside One Rep Max.

Quick note: this guide is for general information only and is not medical advice. If you have a health condition or a result worries you, talk to a qualified clinician.

How to Use This Calculator

Enter your figures into the fields below. One-rep max (1RM) is the heaviest load you can lift once with good form — the reference point for all strength programming.

• Weight lifted: The load on the bar for your test set.
• Reps completed: To near-failure; 2–10 reps works best.
• Unit: kg or lb.

The result appears instantly, with a breakdown of each step. If a figure looks unexpected, double-check your units first — metric versus imperial mix-ups are the most common cause of surprising results.

The One Rep Max Formula

The calculator applies this standard formula:

Epley: 1RM = weight × (1 + reps ÷ 30)
Brzycki: 1RM = weight × 36 ÷ (37 − reps)
Lombardi: 1RM = weight × reps^0.10

• Weight: Load lifted in the test set.
• Reps: Clean reps to near failure (2–10 ideal).
• 1RM: Estimated single-rep maximum.

Epley and Brzycki agree within ~2% for 3–8 reps; the calculator averages the three.

Worked Example

Here is the method applied to realistic figures:

1. Bench press: 80 kg × 6 reps, near failure.
2. Epley: 80 × (1 + 6/30) = 80 × 1.2 = 96 kg.
3. Brzycki: 80 × 36 ÷ 31 ≈ 92.9 kg.
4. Estimated 1RM ≈ 94 kg; hypertrophy work at 70–80% = 66–75 kg.

Frequently Asked Questions

What is one rep max?

The maximum weight you can lift for a single repetition with proper form. It is the standard measure of maximal strength and the basis for percentage-based programming.

Which 1RM formula is best?

Epley is the most popular and accurate for 2–10 reps; Brzycki is close behind. Averaging several formulas smooths individual quirks.

How many reps should I use to estimate 1RM?

Three to six reps to near-failure gives the best accuracy. Beyond 10 reps, muscular endurance contaminates the strength estimate.

Is it safe to test my true 1RM?

For experienced lifters with spotters and good form, yes, occasionally. Beginners and solo lifters should stick to estimated 1RM from submaximal sets.

What percentages should I train at?

Roughly: 85–95% strength, 70–85% hypertrophy, 60–75% endurance, 40–60% warm-up/technique. Most programs live in the 65–85% band.

Rounding is another quiet trap. Round only the final result, never the intermediate steps — early rounding compounds through multi-step calculations and can shift the answer by more than you would expect. Let the calculator keep full precision internally and present the tidy number at the end.

Share the method, not just the answer. When One Rep Max comes up in discussion — with a partner, an adviser, a colleague — walking through the inputs and the worked example builds agreement far faster than quoting a bare figure. People trust numbers they have seen derived; the example section above is your ready-made walkthrough.

Finally, remember that One Rep Max is one instrument on the dashboard, not the whole dashboard. The related guides below connect it to the neighbouring calculations that complete the picture. Readers who follow those links consistently report the same thing: each individual figure makes more sense once you see how they fit together.

It is also worth stressing what One Rep Max cannot do. No calculator captures every nuance of a real situation — unusual circumstances, edge cases and judgement calls still need a human. Use the figure as a strong, evidence-based starting point, and apply common sense (or professional advice) for the last mile. That balance is the mark of someone who uses tools well.

Bookmark this page alongside the calculator itself. Most readers return to One Rep Max calculations at decision points — a change in income, a new goal, an annual review — and having both the tool and the explanation one click away turns each revisit into a thirty-second task instead of a research project.

A useful habit is re-running the One Rep Max calculation whenever your circumstances change — new figures in, fresh answer out. Stale numbers are one of the quietest sources of bad decisions: the maths was right once, but the world moved on. A quick recalculation takes seconds and keeps every downstream decision honest.

If your result surprised you, treat the surprise as information rather than error. Unexpected One Rep Max figures usually point at an input you have been estimating optimistically, a rule you did not know applied, or a genuine change worth investigating. Dig into the breakdown the calculator provides — the ‘why’ is almost always sitting in one specific line.

Consistency beats precision in tracking. Measuring One Rep Max the same way, under the same conditions, on a regular schedule produces trends you can trust — even if any single reading carries a little noise. Pick a routine (monthly, quarterly, whatever fits) and stick to it; the pattern that emerges over time is the real insight.

When the stakes are high — a major financial decision, a medical conversation, a legal or contractual matter — pair the calculator’s output with qualified professional advice. The tool gives you speed and a solid working figure; the professional gives you judgement for your specific situation. Bring your inputs and the result to that conversation and it will be twice as productive.