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Free One-Rep Max (1RM) Calculator

Estimate your one-rep maximum (1RM) — the heaviest single lift you can perform — by entering the weight you lifted and how many reps you completed.

Estimated 1RM (Epley formula)
262.5 lb

Brzycki formula: 253.1 lb

Formula: 225 lb × (1 + 5 ÷ 30) = 262.5 lb

Training weight percentages

% of 1RMWeight (lb)
100%262.5
95%249.4
90%236.3
85%223.1
80%210.0
75%196.9
70%183.8
65%170.6
60%157.5

General information only. Attempting maximal lifts carries injury risk. Consult a qualified coach or sports medicine professional before testing true 1RM loads.

Estimate only. This tool is for general information only and is not medical advice or a diagnosis. Results are estimates based on the formula shown. Consult a qualified healthcare professional for guidance about your own situation.

Quick answer

Your one-rep max (1RM) is the maximum weight you can lift for exactly one full repetition of an exercise. The most widely used estimate is the Epley formula: 1RM = weight × (1 + reps ÷ 30). For example, lifting 225 lb for 5 reps gives an estimated 1RM of about 263 lb. This is an estimate — actual 1RMs vary by lifter, exercise, and fatigue level.

Formula & method

Epley (most common)

1RM = weight × (1 + reps ÷ 30)
  • weight — weight lifted in the working set (lb or kg)
  • reps — number of repetitions completed (best for 1–12 reps)

Accurate for sets of 1–12 reps. Accuracy decreases for very high rep counts (15+).

Brzycki (alternative)

1RM = weight × 36 ÷ (37 − reps)
  • weight — weight lifted in the working set
  • reps — repetitions completed (valid for reps ≤ 36)

Gives results close to Epley for low rep counts; avoid for reps above 12.

Estimated 1RM percentages for common rep counts (Epley)

Reps completed% of 1RM (approx.)
1100%
297%
393%
587%
880%
1075%
1270%

Examples

Example 1: 225 lb for 5 reps
Input
weight = 225 lb, reps = 5
Result
Estimated 1RM ≈ 263 lb
Why
Epley: 225 × (1 + 5 ÷ 30) = 225 × 1.1667 = 262.5, rounded to 263 lb.
Example 2: 100 kg for 3 reps
Input
weight = 100 kg, reps = 3
Result
Estimated 1RM ≈ 110 kg
Why
Epley: 100 × (1 + 3 ÷ 30) = 100 × 1.10 = 110.0 kg.
Example 3: 135 lb for 10 reps
Input
weight = 135 lb, reps = 10
Result
Estimated 1RM ≈ 180 lb
Why
Epley: 135 × (1 + 10 ÷ 30) = 135 × 1.3333 = 180.0 lb.
Example 4: 80 kg for 8 reps
Input
weight = 80 kg, reps = 8
Result
Estimated 1RM ≈ 101 kg
Why
Epley: 80 × (1 + 8 ÷ 30) = 80 × 1.2667 = 101.3, rounded to 101 kg.

When to use this tool

  • Setting percentage-based training loads (e.g., 75% of 1RM for a working set).
  • Tracking strength progress over weeks or months without maxing out every session.
  • Comparing relative strength across body weight using a strength-to-weight ratio.

Common mistakes

  • Using rep counts above 12 — Epley and Brzycki lose accuracy beyond 12 reps per set.
  • Confusing training max with true 1RM. Many programs use 90% of 1RM as a safer working ceiling.
  • Not accounting for fatigue — a set done after heavy warm-ups will underestimate your true 1RM.

Frequently asked questions

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

A one-rep max is the maximum amount of weight you can lift for exactly one full, properly performed repetition of a given exercise. It is the standard measure of absolute strength in powerlifting and strength training.

Which formula does this calculator use?

It uses the Epley formula (1RM = weight × (1 + reps ÷ 30)), which is the most widely cited estimate. It also shows the Brzycki result for comparison. Both are estimates — neither replaces an actual tested maximum.

How accurate is the estimated 1RM?

For sets of 2–6 reps performed to near-failure, the Epley formula is generally within 5–10% of a true tested maximum. Accuracy drops for sets above 12 reps because fatigue and muscular endurance become larger factors than pure strength.

How many reps should I use for the best estimate?

The most reliable estimates come from sets of 3–6 reps taken close to failure. Single-digit rep sets minimize the influence of muscular endurance on the result.

Can I use this for any exercise?

Yes, though it was developed primarily for barbell lifts like the squat, bench press, and deadlift. It may be less accurate for isolation exercises, cable machines, or movements where technique breaks down under heavy load.

Is this medical or fitness advice?

No. This tool is for general information only. Attempting a true one-rep maximum carry real injury risk. Consult a qualified coach or sports medicine professional before testing maximal loads.

Sources & references

External references open in a new tab. We are independent and not affiliated with these organizations.

Disclaimer

This tool is for general information only and is not medical advice or a diagnosis. Results are estimates based on the formula shown. Consult a qualified healthcare professional for guidance about your own situation.

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Last updated: How we calculateReport a correctionDisclaimer

Provided “as is” for general information only — results may be inaccurate, so verify before you rely on them. No warranty; use at your own risk.

Built and reviewed by HIFreeTools against the formula shown above and any authoritative references cited on this page. See our methodology and editorial standards.

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