1RM calculator
One-rep max calculator.
Lift a weight, count the reps. Get your estimated one-rep max from three classic formulas — plus a training percentage table in loadable weights.
How 1RM estimates work.
Your one-rep max is the heaviest weight you can lift once with good form. Testing it directly is risky and exhausting, so lifters estimate it from a heavy multi-rep set using decades-old formulas. LiftLoadout runs three: Epley — weight × (1 + reps ÷ 30); Brzycki — weight × 36 ÷ (37 − reps); and Lander — weight × 100 ÷ (101.3 − 2.67123 × reps). Each has its own bias, so the calculator averages them into one headline number and shows all three.
The percentage table turns that estimate into training loads, rounded to 5 lb so every line is actually loadable at the gym. Estimates are most reliable for 3–8 reps and get shaky above 10 — treat the number as a planning tool, not a guarantee. For the math behind each formula, see the guide 1RM formulas explained.
Worked example
185 lb × 5 reps
Epley: 185 × (1 + 5/30) ≈ 216 · Brzycki: 185 × 36/(37 − 5) ≈ 208 · Lander: 185 × 100/(101.3 − 2.67123 × 5) ≈ 210 · Average ≈ 211 lb.
Common questions.
How accurate is a 1RM estimate?
Formulas predict well for sets of 2 to 5 reps; above 10 reps the error grows quickly. Treat the number as a training target, not a max-out prescription — fatigue, technique, and the lift itself all shift it.
Which formula should I trust?
Epley tends to overestimate, Brzycki to underestimate slightly, and Lander sits between them. LiftLoadout averages all three so no single formula's bias decides your number, and shows each one separately.
What rep range gives the best estimate?
The sweet spot is 3 to 8 reps with good form — heavy enough to be near your max, light enough to complete cleanly. A 1-rep effort simply returns the weight you lifted.
Is it safe to test my real one-rep max?
Max attempts carry real risk. Use the estimate to pick conservative working percentages, warm up properly, and test a true max only with a spotter, safety arms, and experience. The calculator is a guide, not a green light.