How to Calculate Your One-Rep Max (Without Actually Maxing Out)

Your one-rep max is the heaviest weight you can lift for one rep with good form. It’s useful for programming percentages, measuring strength progress, and comparing yourself over time.

The problem is that actually testing a true one-rep max is risky. It puts maximum stress on your joints and connective tissue, and the injury risk goes up with fatigue. Most people don’t need to do it.

Instead, you can estimate your one-rep max from any set of 10 reps or fewer.

The formula

The most commonly used estimation is the Brzycki formula:

Estimated 1RM = Weight / (1.0278 - 0.0278 x Reps)

For example, if you bench press 80 kg for 6 reps:

80 / (1.0278 - 0.0278 x 6) = 80 / 0.861 = 92.9 kg estimated 1RM

The formula is most accurate with sets of 1-6 reps. Above 10 reps, the estimate becomes less reliable because muscular endurance starts to play a larger role than pure strength.

Why estimated one-rep max matters

Even if you never plan to test a real max, tracking your estimated one-rep max over time tells you whether you’re getting stronger.

Here’s why it’s more useful than just tracking weight or reps alone:

• You did 80 kg for 6 reps last month. This month you did 80 kg for 8 reps. Your raw weight didn’t change, but your estimated one-rep max went from 92.9 kg to 98.5 kg. You got stronger.
• You did 80 kg for 8 reps last month. This month you did 85 kg for 6 reps. Different reps, different weight, but the estimated one-rep max went from 98.5 kg to 98.7 kg. Roughly the same strength — you just expressed it differently.

Without the one-rep max estimate, these two scenarios are hard to compare. With it, the comparison is straightforward.

How Logged tracks this automatically

Logged calculates your estimated one-rep max every time you log a set for a weighted exercise. You don’t need to do any math — the app handles it.

In your exercise progress charts, you can see your estimated one-rep max trend over weeks and months. If the line is going up, you’re getting stronger. If it flattens, it might be time to adjust your program.

The app also detects when you hit a new one-rep max personal record, even if you never lifted that weight for a single rep. If your estimated one-rep max for bench press goes from 95 kg to 97 kg based on a set of 5 reps, Logged flags that as a new record.

Tips for accurate estimates

• Use sets of 3-6 reps for the most accurate estimate. Higher rep sets (8-12) still work but introduce more variability.
• Go to near-failure. The formula assumes you couldn’t have done many more reps. If you stopped at 6 reps but had 3 more in the tank, the estimate will be too low.
• Track it over time, not session to session. Any single estimate might be off by a few percent. The trend across weeks is what matters.

What to read next

• Progressive Overload: The Simple System to Get Stronger — how to use your logged data to make sure your estimated one-rep max keeps climbing.
• Why You Need a Workout Log (And How to Start) — the case for tracking every set, which makes one-rep max estimation possible.