HABBEAT

One-Rep Max (1RM) Calculator

How it works

Estimate max strength from a submaximal set

Estimated one-rep max

Enter the weight you lifted on the set — not your body weight.

Estimated 1RM

70.0 kg

≈ 154.3 lb

Working weights from this 1RM

50%
35.0 kg
60%
42.0 kg
70%
49.0 kg
75%
52.5 kg
80%
56.0 kg
85%
59.5 kg
90%
63.0 kg
95%
66.5 kg

About this tool

A one-rep max (1RM) is the heaviest load you could lift once with solid technique. Testing true 1RMs is taxing and risky if form breaks down.

Submaximal estimators like the Epley formula let you predict 1RM from a set of several reps, then prescribe training as percentages of that estimate.

Estimates work best with controlled reps (not grinding failure with broken form) and tend to be less accurate as rep counts climb past ~10–12.

How it works

  1. Enter the weight on the bar (or machine stack) and how many clean reps you completed (1–15).
  2. We apply the Epley formula: weight × (1 + reps / 30).
  3. Use the estimate to set working sets (e.g. 70–85% for hypertrophy/strength blocks) — and re-test periodically as you progress.

Practical tips

  • Warm up thoroughly before heavy sets; estimates assume the set was representative, not a messy grind.
  • Use the same standard of depth/ROM every time you re-estimate.
  • If you train with machines, keep estimates machine-specific — they don’t always transfer to free weights.

Frequently asked questions

What is the Epley formula?

Estimated 1RM = weight × (1 + reps / 30). Other formulas (Brzycki, Lombardi) exist; Epley is a popular default for mid-rep ranges.

Should I test a true 1RM?

Only if you are experienced, well spotted, and the program calls for it. Many lifters progress fine with estimated maxes and RPE.

Why limit reps to 15?

High-rep sets drift further from true max strength and inflate error. For endurance sets, track load × reps instead of chasing a 1RM.

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Disclaimer: These tools provide general estimates only. They are not medical advice. For health conditions, pregnancy, or personalised nutrition, speak with a qualified professional.