How to Calculate Your e1RM (Estimated 1 Rep Max)

You Don't Need to Max Out to Know Your Max

Testing a true 1 rep max is taxing, risky on technical lifts, and only relevant if you're actually competing. For everyone else, the estimated 1 rep max (e1RM) gives you the same information without the recovery cost.

The Epley Formula

The most widely used e1RM formula was developed by Boyd Epley in 1985:

e1RM = weight × (1 + reps / 30)

So if you bench 80kg for 8 reps:

e1RM = 80 × (1 + 8/30) = 80 × 1.267 = 101.3kg

Your estimated 1 rep max is approximately 101kg. ForgeLifting calculates this automatically for every logged set.

Why e1RM Matters for Tracking Progress

Raw weight and reps don't tell you whether you're getting stronger across different set and rep ranges. e1RM normalises everything to a single number. If your bench e1RM goes from 85kg to 95kg over three months — regardless of whether you're running 5x5, 3x8, or 4x12 — you're getting stronger.

This is why ForgeLifting tracks e1RM per exercise and shows you a trend chart. Month-to-month e1RM movement is the most honest signal of real strength progress.

Using e1RM to Set Training Weights

Many programmes (including 5/3/1) prescribe training weights as percentages of your 1RM. If you don't know your actual max, use your e1RM:

• 75% of 100kg e1RM = 75kg
• 85% of 100kg e1RM = 85kg

Start slightly conservatively (e.g. treat your e1RM as 95% of actual) to account for formula variance.

The Bottom Line

e1RM is the most practical strength metric for natural, non-competitive lifters. Log your sets consistently, let the formula do the work, and watch the number move over time.