What is a 1RM (one-rep max)?

Your one-rep max (1RM) is the maximum weight you can lift for a single repetition with proper form on a given exercise. Estimated 1RM is calculated from a sub-maximal set (e.g. 5 reps at 80% of max) using a formula like Epley, Brzycki, or Lombardi to predict what your true single-rep max would be.

What is the Epley formula for 1RM?

The Epley formula is: 1RM = weight × (1 + reps / 30). It is the most commonly used estimated one-rep max formula, used in research and most strength training apps.

Which 1RM formula is most accurate?

All six formulas (Epley, Brzycki, Lombardi, O'Conner, Wathan, Mayhew) produce similar results in the 2–10 rep range. Epley and Brzycki are the most widely used. Above 10 reps, accuracy of all formulas drops because muscular endurance starts dominating over pure strength.

Should I actually test my 1RM?

Most lifters don't need to. Estimated 1RM from a 3–8 rep set is accurate enough for tracking progression and programming percentages. True 1RM testing carries injury risk and is generally reserved for powerlifters peaking for a meet.

How do I track my 1RM over time?

Log your sets each session and compute estimated 1RM from your best set. Tools like StrengthInsight do this automatically from a workout screenshot — extracting your sets, reps, and weights and plotting estimated 1RM trends per exercise so you can see whether you're getting stronger.

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Free Calculator

1RM Calculator — Estimated One-Rep Max

Six formulas (Epley, Brzycki, Lombardi, O'Conner, Wathan, Mayhew) · Free · No signup

Enter the weight and reps from any set. Your estimated one-rep max is calculated instantly using six leading 1RM formulas plus a percentage table for programming.

Weight lifted

Reps performed

Unit

Estimated 1RM (average of 6 formulas)

— kg

Based on weight × reps using Epley, Brzycki, Lombardi, O'Conner, Wathan and Mayhew.

Epley—

Brzycki—

Lombardi—

O'Conner—

Wathan—

Mayhew—

Training percentages (from your estimated 1RM)

%	Weight	Typical use
95%	—	2–3 RM, peaking
90%	—	3–5 RM, strength
85%	—	5–6 RM, strength
80%	—	6–8 RM, strength/hypertrophy
75%	—	8–10 RM, hypertrophy
70%	—	10–12 RM, hypertrophy
65%	—	12–15 RM, volume
60%	—	Warm-up / endurance

How is 1RM calculated?

Estimated 1RM (one-rep max) is your predicted maximum lift for a single repetition, calculated from a sub-maximal set. Each formula handles the weight × reps relationship slightly differently, but they all produce similar results in the 2–10 rep range.

The six formulas, explained

Epley: 1RM = weight × (1 + reps / 30). The most commonly used formula.
Brzycki: 1RM = weight × 36 / (37 − reps). Slightly more conservative than Epley above 5 reps.
Lombardi: 1RM = weight × reps^0.10. A power-curve approach.
O'Conner: 1RM = weight × (1 + 0.025 × reps). The most conservative of the six.
Wathan: 1RM = (100 × weight) / (48.8 + 53.8 × e^(−0.075 × reps)). Exponential decay model.
Mayhew: 1RM = (100 × weight) / (52.2 + 41.9 × e^(−0.055 × reps)). Designed from bench press data.

The calculator above shows all six and averages them — averaging smooths out the differences and produces a robust estimate.

How accurate is estimated 1RM?

For sets in the 2–10 rep range, all six formulas are typically within 2–5% of true 1RM. Above 10 reps, accuracy degrades rapidly because muscular endurance starts dominating over pure strength capacity — a 20-rep set tells you more about conditioning than maximal force.

For tracking progression, estimated 1RM is more useful than chasing true 1RM tests. Test 1RMs are infrequent, taxing, and carry injury risk. Estimated 1RM updates every session, so you see strength trends week-to-week without ever needing to attempt a max.

How to use 1RM in programming

Most strength programs prescribe loads as a percentage of 1RM:

Strength block: 80–95% of 1RM, low reps (1–6), longer rest
Hypertrophy block: 65–80% of 1RM, moderate reps (6–12), moderate rest
Volume / metabolic block: 50–70% of 1RM, higher reps (12–20)

Use the percentage table above to translate your estimated 1RM directly into working weights for any of these zones.

Should you track 1RM over time?

Yes — but estimated, not tested. The cleanest way is to log every session, take your best set, compute estimated 1RM, and chart the trend per exercise. A flat line for 4+ weeks signals a plateau; a rising line is real strength progress.

This is exactly what StrengthInsight automates: upload a screenshot of your WHOOP Strength Trainer or Hevy session and the app extracts your sets, computes estimated 1RM per exercise, and plots the trend over time. No manual logging, no spreadsheet.

See your estimated 1RM trend, automatically

StrengthInsight reads your WHOOP Strength Trainer or Hevy screenshots and builds per-exercise estimated 1RM charts, PR tracking, and plateau alerts — free.

Try StrengthInsight free →

FAQ

What is a 1RM?

Your one-rep max — the heaviest weight you can lift for a single rep with proper form. Estimated 1RM predicts that number from a sub-maximal set without you actually having to attempt a true max.

Which formula should I use?

For most lifters, Epley or Brzycki are the standards. The calculator above shows all six and averages them — that's the most robust single number.

How often should I recalculate my 1RM?

Every session. Take your best set (highest weight × reps) and compute estimated 1RM. Tracked over weeks, this is the cleanest single number for whether a lift is progressing.

Can I trust the estimate at very high reps?

Above ~10 reps, accuracy drops. The estimate becomes more about endurance than max strength. Stick to 2–10 rep sets for reliable 1RM predictions.