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Updated 2026 · By ToolFern

One Rep Max Calculator

Estimate your one rep max from a normal working set. Enter the weight you lifted and how many reps you managed, and this tool shows your 1RM using both the Epley and Brzycki formulas, plus a table of training loads, all calculated privately in your browser.

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Estimated 1RM (Epley)
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Estimated 1RM (Brzycki)

Training loads (from the Epley 1RM)

% of 1RMLoad
95%-
90%-
85%-
80%-
75%-
70%-

These are estimates from a single set, not a tested max. Accuracy is best at low reps and drops above about 10 reps. Warm up properly and use a spotter before attempting a true one rep max.

How to use this one rep max calculator

  1. Weight lifted, enter the load you used and pick your unit (kg or lb).
  2. Reps performed, enter how many clean reps you completed with that weight (1 to 15).
  3. Read your estimated 1RM from each formula and use the training load table, everything updates instantly as you type.

Nothing is submitted or stored: your numbers never leave your device, so you can log and compare sets privately.

How 1RM is estimated

A one rep max is the most weight you can lift for a single repetition. Rather than attempting a risky true max, you can estimate it from a set you already did. This calculator uses two of the most common formulas:

Both formulas agree closely at low rep counts and diverge a little as the reps climb. They are most accurate for heavy sets of about 1 to 5 reps, reasonable up to around 10, and get less accurate above roughly 10 reps, where stamina and pacing affect the result as much as raw strength. Use the higher of the two as a working ceiling or the lower as a conservative target, whichever suits your training.

Using the training load table

The percentage table builds working weights from your Epley 1RM. Strength work usually sits around 85 to 95 percent of your max for low reps, while hypertrophy and volume blocks often live near 70 to 80 percent. Pick the percentage that matches your goal for the day and the table gives you the load to put on the bar.

Note: these figures are estimates, not a tested maximum. Treat them as a starting point, warm up properly, and use a spotter or safety bars before attempting heavy singles.

Frequently asked questions

Which formula should I trust, Epley or Brzycki?

Both are widely used and close at low reps. Many lifters average the two or use Brzycki, which tends to read slightly lower at higher reps. For a single set under about 5 reps the difference is small.

Why does accuracy drop at high reps?

Above about 10 reps, muscular endurance and pacing influence how many reps you hit, so the estimate drifts further from your true single rep strength. Keep test sets heavy for the best read.

Does it work in pounds?

Yes, switch the unit to lb. The estimate and the whole training load table are shown in the unit you choose.

Is my data uploaded?

No, everything is calculated on your device and nothing is sent anywhere.