How to Calculate Your 1 Rep Max Without Maxing Out

Last updated: May 2026

To calculate your 1 rep max, take any weight you can lift for 3–10 reps and plug the numbers into an estimation formula. You don’t need to attempt a true maximal single. The two most widely used formulas — Epley and Brzycki — produce estimates accurate to within 3–5% for most compound lifts when your rep count is kept between 2 and 10.

Below you’ll find both formulas with worked examples, a comparison of all major 1RM estimation methods, and when an estimated 1RM is sufficient versus when you actually need to test.

The Two Main Formulas

Both formulas take the same two inputs: the weight lifted and the number of reps completed.

Epley (1985): 1RM = Weight × (1 + Reps ÷ 30)

Brzycki (1993): 1RM = Weight × (36 ÷ (37 − Reps))

Epley tends to produce slightly higher estimates and is the more commonly cited formula. Brzycki is more conservative and is often considered more accurate in the 2–10 rep range. For practical programming, either works — the difference between them is rarely more than 5 lb.

All Major 1RM Estimation Formulas

Formula	Equation	Best For
Epley (1985)	Weight × (1 + Reps / 30)	General use; most widely cited
Brzycki (1993)	Weight × (36 / (37 – Reps))	Accuracy in the 2–10 rep range
Lander (1985)	(100 × Weight) / (101.3 – 2.67 × Reps)	Powerlifting; performs well 1–10 reps
O’Conner et al. (1989)	Weight × (1 + 0.025 × Reps)	Conservative estimate; low rep counts
Lombardi (1989)	Weight × Reps^0.10	Alternative calculation; less common

All formulas assume that reps are performed close to failure. If you stopped at 8 reps when you could have done 12, the formula will underestimate your true 1RM.

Step-by-Step: Estimating Your 1RM

Step 1 — Choose a working weight. Select a load you can lift for 3–10 reps with solid technique. You should reach near-failure on the set — stop when you have 0–1 reps left, not when the set starts feeling heavy.

Step 2 — Perform the set to near-failure. Maintain form throughout. If technique breaks down at rep 6, stop at 5. Record the exact weight and rep count immediately after the set.

Step 3 — Apply the formula. Run both Epley and Brzycki. If they’re close (within 5 lb), use the lower number. If they diverge by more, recheck that your set was actually at near-failure.

Step 4 — Round to a loadable weight. Round your estimated 1RM to the nearest 5 lb (2.5 kg). Working with a number like 231.4 lb adds false precision to a population-average formula.

Worked Examples

Example 1: Bench Press

You bench press 185 lb for 8 reps at near-failure.

Epley: 185 × (1 + 8/30) = 185 × 1.267 = 234 lb → round to 235 lb

Brzycki: 185 × (36 / (37–8)) = 185 × (36/29) = 185 × 1.241 = 230 lb → round to 230 lb

Estimated 1RM: 230–235 lb. Use 230 lb for programming (conservative).

Example 2: Squat

You squat 265 lb for 5 reps at near-failure.

Epley: 265 × (1 + 5/30) = 265 × 1.167 = 309 lb → round to 310 lb

Brzycki: 265 × (36 / (37–5)) = 265 × (36/32) = 265 × 1.125 = 298 lb → round to 300 lb

Estimated 1RM: 300–310 lb. Use 300 lb for programming.

Example 3: Deadlift

You deadlift 315 lb for 3 reps at near-failure.

Epley: 315 × (1 + 3/30) = 315 × 1.100 = 347 lb → round to 345 lb

Brzycki: 315 × (36 / (37–3)) = 315 × (36/34) = 315 × 1.059 = 334 lb → round to 335 lb

Estimated 1RM: 335–345 lb. Use 335 lb for programming.

Accuracy and Limitations

Estimation formulas are accurate to within 3–5% for most compound lifts when the rep count is 2–10. Three factors degrade accuracy:

• High rep counts (12+): Metabolic fatigue increasingly limits performance beyond 10 reps, independent of maximal strength. Formulas tend to overestimate 1RM at high rep counts.
• Muscle fiber type: Slow-twitch dominant lifters can complete more reps at a given percentage of their 1RM than average. For these lifters, the formula may underestimate their true 1RM.
• Incomplete effort: If you didn’t push close to failure, the formula reflects what you demonstrated, not your true capacity. The estimation is only as good as the effort put into the test set.

A 5% error in your estimated 1RM means your programmed training weights are within one zone of the intended percentage — rarely a meaningful practical difference for intermediate lifters.

Estimated vs Tested 1RM

	Estimated 1RM	Tested 1RM
Injury risk	Low	Higher
Accuracy	±3–5%	Exact (on that day)
Fatigue cost	Minimal	3–5 days recovery
Best use case	Ongoing programming	Competition prep, peaking
Experience required	Any level	Solid technique required

For most intermediate lifters, estimated 1RM is the right tool. You can update it every few weeks from your working sets without adding a dedicated testing session. Reserve true 1RM testing for the end of a peaking block when it serves a specific purpose — not as a routine progress check.

Frequently Asked Questions

What is the most accurate 1RM estimation formula?

Research comparing estimation formulas consistently finds that Brzycki and Epley perform similarly for compound lifts in the 2–10 rep range, with typical errors of 1–5%. Neither is definitively more accurate across all lifts and populations. For practical programming, the formula matters far less than performing your test set close to actual failure.

Can I calculate 1RM from just 1 heavy rep?

If you perform a heavy single that isn’t a true maximum — for example, a rep that took 4–5 seconds to complete and you couldn’t have done a second — you can plug 1 rep into the formula. Epley gives: 1RM = Weight × (1 + 1/30) = Weight × 1.033. That’s a 3.3% increase above what you lifted. At this point you’re essentially at your 1RM already, so the estimate adds little value.

How do I calculate 1RM for the deadlift specifically?

The same formulas apply. The deadlift is best tested at 2–5 reps due to the high technical and fatigue demands of the movement. Testing at higher rep counts introduces more technique degradation and fatigues the posterior chain before you’ve gotten a clean measure.

Is it safe to test my 1RM?

Testing a true 1RM is safe for experienced lifters with solid technique and an appropriate warm-up protocol. For beginners or lifters newer to a specific movement pattern, estimation from working sets is the better approach — it carries no more risk than a normal training set and provides accurate enough data for programming purposes.