The Epley Formula Explained: Estimate Your One-Rep Max With Examples

Published 24 October 2026 · 7 min read

A true one-rep max test can be demanding, but the Epley formula can estimate your maximum from a weight you’ve lifted for several reps. The calculation is quick and useful for planning strength training. Still, it’s an estimate, not a promise of what you can lift today. Here’s how to work it out, apply it to training, and keep the result in perspective.

Calculate Your Estimated One-Rep Max With the Epley Formula

The Epley formula estimates the most weight you could lift for one repetition, based on a weight and the number of reps you completed. Since it predicts rather than tests your one-rep max, the result is often called an estimated 1RM, or e1RM.

Use the Epley formula: load × (1 + reps ÷ 30)

The formula is estimated 1RM = weight lifted × (1 + number of repetitions ÷ 30). “Weight lifted” means the load used for the set, while “repetitions” means the number of completed reps with that load.

For example, if you lifted 100 kg for 8 reps, enter 100 as the weight and 8 as the reps. Keep the same unit, such as kilograms or pounds, throughout the calculation.

See how repetitions change the estimate

In this formula, more reps at the same weight produce a higher estimated 1RM. For example, 100 kg for 3 reps gives an estimate of 110 kg, while 100 kg for 8 reps gives about 126.7 kg.

That change comes from the equation’s set relationship between load and reps. It doesn’t mean every lifter’s strength follows that exact pattern.

Know what the estimate can—and cannot—tell you

A tested 1RM is the heaviest load you successfully lift once under the test conditions. An estimated 1RM is a prediction based on a different set, so it can’t confirm what you’re able to lift on a given day.

Use the number to help plan or track training, not as a guarantee. Sleep, fatigue, technique, and other factors can affect your performance.

Follow Worked Examples to Check the Epley Calculation

The key is to place the load and rep count in the correct parts of the formula. These examples show the arithmetic; they aren’t claims about any real lifter’s ability.

Estimate a 1RM from 100 kilograms for 8 repetitions

Start with the Epley formula and substitute the values: 100 × (1 + 8 ÷ 30). First, 8 divided by 30 is about 0.267. Then multiply 100 by 1.267 to get 126.7 kg, or about 127 kg.

Rounding makes the result easier to read, but the estimate remains approximate. It doesn’t mean you should load 127 kg and attempt a max lift.

Estimate a 1RM from 135 pounds for 5 repetitions

Use pounds for both the load and the result: 135 × (1 + 5 ÷ 30). Five divided by 30 is about 0.167, so the calculation is 135 × 1.167 = 157.5 lb.

The estimated 1RM is 157.5 lb. Don’t convert only one part of the calculation to kilograms; keep the units consistent.

Avoid common calculation mistakes

Mixing pounds and kilograms, entering the wrong load, or typing the rep count incorrectly can change the answer. Another common error is treating the result as an exact, tested maximum.

Check the numbers before logging your estimate. If you track several lifts, a calculator or spreadsheet can help keep the math consistent.

Use the Estimate to Make Training Decisions

An estimated 1RM can give you a reference point for training. How you use it depends on your program, since plans may set loads in different ways.

Calculate a percentage-based training load

Some programs prescribe a load as a percentage of your 1RM. For example, if your estimated 1RM is 157.5 lb and your plan calls for 70%, the calculation is 157.5 × 0.70 = 110.25 lb. You might round that to a practical plate load if your program allows it.

Follow the percentage your plan sets. There’s no single percentage that fits every program or training goal, and some plans base loads on a separate training max.

Track progress consistently over time

Compare estimates for the same exercise under similar conditions. Use the same equipment, technique standards, and approach to effort when you can.

A higher estimate may point to progress, but it can also reflect a different level of fatigue or a change in how you performed the set. Look at the trend across repeated sessions rather than reading too much into one result.

Choose a suitable set for estimating

Use a controlled set with a recorded load and clear rep count. The set should be challenging and close to your limit; an easy set stopped well short may not offer a useful estimate of your rep capacity.

Keep your technique consistent from rep to rep. Don’t add partial or compromised reps just to raise the number.

Understand Where the Epley Formula Can Be Less Reliable

The formula is a convenient estimate, but it can’t account for every lifter or exercise. Treat its result as a guide, not a precise measure.

Recognize that estimates vary between people and lifts

People can differ in how many reps they can perform at a given share of their maximum. Training experience and the exercise itself can also affect how well a rep-based estimate matches a tested 1RM.

A formula that seems useful for your bench press may give a different level of accuracy for your squat. Use estimates most carefully when comparing different lifts or lifters.

Treat high-repetition sets with extra caution

As reps rise, muscular endurance and pacing can have more influence on how the set goes. That can make the estimated 1RM less representative of a single heavy lift.

A 2006 study of chest press and leg press found that 5-rep maximum tests predicted 1RM more accurately than 10- or 20-rep tests. The study by Reynolds, Gordon, and Robergs also found that Epley was among several formulas with similar results when applied to 5-rep data. Those findings don’t set a universal cutoff for every lift or person.

Compare formulas without assuming one is always best

Other equations, such as the Brzycki formula, estimate a 1RM from load and reps too. They may return a different number from the same set because they use a different calculation.

No one formula is guaranteed to be the best choice in every case. If you compare estimates, use the same formula each time so your records stay consistent.

Apply the Formula Safely and Keep the Result in Perspective

An estimate can support training decisions, but it doesn’t replace good lifting habits. Keep form and safe setup ahead of a bigger number.

Prioritize sound technique over a higher estimate

Count only reps completed with the range of motion and form you intended to use. Shortened or altered reps can distort the calculation and make future comparisons less useful.

Stop the set if your technique breaks down. A lower estimate based on clean reps is more useful than a higher number built on compromised form.

Use a spotter and appropriate equipment when testing a true max

An estimate doesn’t make a true 1RM attempt safe by itself. If you choose to test a maximum, follow your gym’s safety rules and use a spotter or safety arms where appropriate.

A qualified coach can help with setup, technique, and load choices. Don’t attempt a max lift just to see whether an estimate is exact.

Record the context alongside the number

Log the exercise, load, reps, and date with each estimate. Note relevant details such as equipment changes or unusual fatigue, especially when you compare results later.

A simple record helps you judge whether two estimates came from similar conditions. It also makes it easier to spot a steady trend over time.

Conclusion: Keep Your Epley Estimate in Perspective

The Epley formula estimates a one-rep max with weight × (1 + reps ÷ 30). The worked examples show how to calculate it, while its limits explain why the result isn’t a guaranteed maximum. Use clean reps, consistent conditions, and your program’s prescribed loads to guide training. Log your next estimate, then compare it with future sets performed under similar conditions.