How to Estimate Your 1RM Without Maxing Out

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Testing your one-rep max (1RM) is the gold standard for measuring strength, but it’s also risky, time-consuming, and psychologically taxing. Going for a true max attempt means loading a barbell with more weight than you’ve ever lifted and hoping for the best. For most lifters — especially those training without a spotter — that’s a recipe for injury.

The good news: you can estimate your 1RM with high accuracy using a lighter set and a simple formula. Research by LeSuer et al. (1997) validated four equations against actual max tests in 67 participants, and the results show that submaximal estimation works remarkably well — when you use the right rep range.

The Four Formulas

Each formula takes your weight and reps and extrapolates to a predicted maximum:

Epley (1985): weight × (1 + reps / 30) The most widely used formula. Optimized for 2–8 reps. If you benched 225 lbs for 5 reps, the Epley formula predicts a 1RM of 225 × (1 + 5/30) = 262.5 lbs.

Brzycki (1993): weight × 36 / (37 − reps) Most accurate at 1–6 reps. Slightly more conservative than Epley at higher rep ranges. The same 225×5 set gives 225 × 36 / 32 = 253.1 lbs.

O’Conner (1989): weight × (1 + 0.025 × reps) A gentler per-rep increment. Best in the 2–8 rep range. For 225×5: 225 × 1.125 = 253.1 lbs.

Lombardi (1989): weight × reps^0.10 Uses an exponential model rather than linear scaling. Most accurate at 2–10 reps. For 225×5: 225 × 5^0.10 = 264.3 lbs.

The differences between formulas are small at low rep ranges and grow wider as reps increase. This is why the sweet spot for estimation is 1–5 reps — all four formulas converge within ±2–4% of your true 1RM.

When to Trust the Estimate

The accuracy of each formula depends on how many reps you perform:

• 1–5 reps (high confidence): Estimates are within ±2–4% of actual 1RM. This is the sweet spot. If you want a reliable number, work in this range.
• 6–10 reps (moderate confidence): Estimates within ±4–7%. Still useful, but consider retesting with a heavier set for a tighter number.
• 11–15 reps (low confidence): Estimates within ±8–15%. The formulas start to diverge significantly. Use this as a rough guideline only.
• 15+ reps (unreliable): Error margins exceed 15%. Don’t base programming decisions on these estimates.

The Deadlift Exception

Here’s something most calculators don’t tell you: all four formulas underestimate deadlift by approximately 10%. LeSuer et al. found that Epley underestimated deadlift by 10.3%, Brzycki by 11.6%, and O’Conner by 13.6%.

Why? The deadlift has a longer range of motion and a different strength curve compared to the squat or bench press. The lockout portion of the deadlift is particularly hard to predict from submaximal sets because most lifters fail at lockout, not off the floor.

The fix: multiply your deadlift estimate by 1.10 for a more realistic number. If the calculator says your deadlift 1RM is 405 lbs, your true max is probably closer to 445 lbs.

RPE and Reps in Reserve

If you know the Rate of Perceived Exertion (RPE) of your set, you can improve the estimate by accounting for reps in reserve (RIR). The adjustment is simple:

effective reps = actual reps + (10 − RPE)

So 5 reps at RPE 8 (meaning you could have done 2 more) is treated as 7 effective reps. This gives the formulas more data to work with and produces a more accurate prediction, especially useful when you’re not going to failure.

Using Training Max Percentages

Once you have your estimated 1RM, you can set training intensities using percentages. Most strength programs don’t have you lift at 100% every session — instead, they use a “training max” that’s 85–90% of your actual max:

Percentage	Use Case
65%	Warm-up sets, volume work
70%	Hypertrophy sets (8–12 reps)
75%	Strength-endurance (6–8 reps)
80%	Strength work (4–6 reps)
85%	Heavy singles practice (2–3 reps)
90%	Training max in 5/3/1 and similar programs
95%	Peaking phase (1–2 reps)

Using a training max instead of your true max gives you room to progress. When you hit all your reps at 90% for a given set/rep scheme, you bump the training max up and work again.

Practical Example

Say you squat 275 lbs for 3 reps at RPE 9:

1. Effective reps: 3 + (10 − 9) = 4
2. Epley: 275 × (1 + 4/30) = 311.7 lbs
3. Brzycki: 275 × 36 / 33 = 300 lbs
4. O’Conner: 275 × (1 + 0.025 × 4) = 302.5 lbs
5. Lombardi: 275 × 4^0.10 = 325.2 lbs
6. Average: ~309.9 lbs
7. Training max (90%): ~278.9 lbs

Your working weights for the week might be: 224 lbs (80%), 237 lbs (85%), 251 lbs (90% as training max).

Try the Calculator

Use our free 1-Rep Max Calculator to get instant estimates from all four formulas. Enter your weight, reps, and optional RPE — the calculator handles the rest, including deadlift correction and confidence bands.

Key Takeaways

• Test with 1–5 reps for the most accurate estimates (±2–4%)
• Apply a 1.10× correction for deadlift
• Use RPE to account for reps in reserve
• Set training max at 85–90% of estimated 1RM
• Retest every 4–6 weeks as you get stronger