How to Calculate Your One-Rep Max: Formula, Example, and Simple Tracker

To calculate an estimated one-rep max, multiply the weight you lifted by 1 + (reps ÷ 30). This is the Epley formula:

estimated 1RM = weight × (1 + reps ÷ 30)

For example, 100 kg for 5 reps estimates to 116.7 kg:

100 × (1 + 5 ÷ 30) = 116.7

That number is an estimate, not a promise of what you can lift for one rep today. It is most useful when you calculate it from comparable working sets and watch the trend for the same exercise. You can use the template below in a notebook or spreadsheet, then keep the same records in a workout log.

How to calculate one rep max from a working set

Use a completed set with a known load and rep count. Keep the exercise and setup specific. A bench press estimate does not transfer to an incline press, and a machine setting may not compare cleanly between gyms.

1. Record the load and completed reps from a controlled working set.
2. Divide the reps by 30.
3. Add 1.
4. Multiply that result by the load.
5. Round the result to a practical increment for your equipment.

Here is a worked example in pounds. If you performed 185 lb for 8 reps:

185 × (1 + 8 ÷ 30) = 234.3 lb

Round that to about 234 lb, or to the nearest loading increment you would actually use. The formula is unit-agnostic, so it works with kilograms or pounds as long as you keep the same unit throughout the calculation.

A simple one-rep max tracker you can copy

Use one row per comparable top working set. The useful part is the context: the variation, the load, the reps, and whether the set was broadly comparable to last time.

This example shows why the estimated 1RM is a helpful second view of a log. The heaviest set is not automatically the best comparison. The 100 kg x 6 set estimates slightly higher than 102.5 kg x 5, but neither entry says anything definitive about a true max. Use the pattern to inform your next training decision, not to declare a result from one calculation.

When is an estimated one-rep max useful?

An estimate is useful when you want a consistent reference without regularly attempting maximal singles. It can help you compare similar sets over several weeks, sanity-check percentage-based programming, or see whether a familiar lift is moving in the direction you want.

For a fair comparison, hold as much as you can constant:

• Use the same exercise variation and similar equipment.
• Record only completed work, not a planned set that changed mid-session.
• Keep the same unit of measurement.
• Note unusual changes that affect the comparison, such as a different bar, range of motion, or a long break from the exercise.
• Look at several entries, not one unusually good or poor day.

A true 1RM test can be a reliable strength assessment when it is appropriately administered. A systematic review of 32 studies found generally high test-retest reliability, while also reporting variation between studies and tests. That is another reason to treat an equation-based result as an estimate rather than a diagnosis or a guarantee. Read the review on PubMed.

What rep range should you use for the Epley formula?

For this workflow, use a set in the range PeakBFF documents for its historical estimate: 1 to 10 reps. A one-rep set is simply its loaded weight. For multiple reps, the formula adjusts the load upward. The farther your set moves from a heavy, repeatable working set, the more outside factors can dominate the result: conditioning, technique drift, rep speed, and how close you were to failure.

That does not make a higher-rep set useless. It just makes it a less clean proxy for a maximum-strength number. Compare like with like whenever you can. If your program specifies an actual test, follow the program's instructions, use equipment and supervision appropriate to the lift, and do not attempt a load you cannot control safely.

How PeakBFF turns a logged set into a 1RM estimate

PeakBFF's exercise history shows a personal-record strip for weight-and-reps exercises. It calculates the best Epley estimated 1RM from completed working sets and keeps the heaviest logged set alongside it. Tap the strip to open the one-rep max calculator. It pre-fills the best set when one exists, lets you adjust the weight and reps, and shows estimated working weights at 95%, 90%, 85%, 80%, 75%, 70%, and 65%.

That is a useful workflow when your real job is not a one-off calculation but keeping your training record usable:

1. Log your completed weight-and-reps sets during the workout.
2. Open that exercise's History tab after the session.
3. Check the estimated 1RM and heaviest set together.
4. Tap the personal-record strip if you want to test a different load and rep input or view the working-weight table.
5. Compare the next like-for-like session before deciding whether to progress.

PeakBFF stores workout loads metrically and displays the calculator in your chosen kg or lb setting, so the calculation stays in the unit you train with. For the wider progression rule behind those next-session decisions, use our simple progressive-overload template.

Do not let the estimate replace your training log

An estimated one-rep max is only one signal. A log that also keeps the exercise, working sets, reps, load, and context is easier to act on than a single headline number. If you are training for muscle, weekly hard-set context may be more actionable than chasing a maximum. Our weekly sets per muscle template is a practical companion for that view.

If you want one place to log sessions, see exercise history, and keep a simple Epley estimate tied to the actual sets that produced it, download PeakBFF for iOS or Android. For a broader app choice, see our best gym tracker apps comparison.