One Rep Max Calculator (1RM)

What is a one-rep max (1RM)?

Your one-rep max — 1RM — is the most weight you can lift once with good form. It is the reference unit that percentage-based strength programs are written in: when a program says “work at 80% of your max,” it needs a max to work from. This free one rep max calculator estimates that number from a set you have already done, for any lift, so you never have to attempt a risky true single to program your training.

Why your 1RM matters

A 1RM is the anchor for percentage-based programming (5/3/1, 5×5, linear progression), a clean way to track progress over time, and a fair way to compare strength across lifters of different bodyweights. Get the number once and the whole training week falls out of the percentage table below.

How to find your 1RM — two ways

Estimate it (recommended, safer)

Do a hard set of 3–6 reps, enter the weight and reps above, and read your estimated max. This is the fast, low-risk path — no spotter, no all-out single — and for most lifters it is accurate enough to program around. If you already know your max, switch to “I know my 1RM” and the tool skips straight to the training tables.

Test it directly

If you want a true number, ramp up with the warm-up sets and take progressive attempts to a single. Safety first: warm up thoroughly, use a rack with safety arms or a spotter, and — if you are a beginner — estimate rather than max. A missed max on bench or squat alone is genuinely dangerous.

How to use this calculator

1. Pick your lift (or leave it on “Any lift”).
2. Enter a weight and reps from a recent hard set — 3–6 reps is ideal.
3. Read your estimated 1RM, then use the %-of-1RM table to set working loads.

The 1RM formulas — comparison

There is no single correct 1RM equation; there are several regression formulas fit to different data. This tool shows five and defaults the headline to the average of Epley and Brzycki, because at low reps Brzycki reads low and Epley reads high, so their mean cancels the directional bias (LeSuer 1997). Worked example: 225 lb × 5 → Epley 262.5, Brzycki 253.1, average ≈ 258. The equations trace to Epley (1985) and Brzycki (1993); Wathan is often the single most accurate across bench, squat and deadlift (LeSuer 1997). Open “Show all 5 formulas” to see the full spread.

How accurate is a 1RM estimate?

Roughly ±3% when reps are in the 2–10 range, most accurate at ≤6 reps, and degrading sharply above ~10 reps (LeSuer 1997; Reynolds 2006 found the 5RM set most accurate). Individual leverages and bar speed shift the number, so read it as an estimate from published formulas, not a measured max.

Methodology & sources

The headline 1RM is the mean of the Epley and Brzycki equations; the “show all 5 formulas” panel adds Lombardi, O’Conner and Wathan. Accuracy figures come from LeSuer et al. 1997 (JSCR 11(4):211–213) and Reynolds et al. 2006. Training-zone framing (≥80% 1RM for strength; training to failure not required) follows the ACSM 2026 resistance-training position stand — used for load and volume prescription only, never for the 1RM formulas. Strength standards are drawn from Kilgore / ExRx published norms.

How to use % of your 1RM to program

The training table turns your max into loads: strength at 85–100%, hypertrophy 65–80%, endurance and speed below 65% (ACSM 2026 position stand). These map onto any percentage program — read the load for your target intensity and go.

Why is the estimate the same for every lift?

If you switch the lift selector and the estimated 1RM doesn’t change, that’s expected — and it’s how every 1RM calculator works. The prediction formulas (Epley, Brzycki and the rest) use only weight and reps; they have no term for which exercise you did, so 225 × 5 returns the same raw number whether you label it bench, squat, or deadlift. The exercise doesn’t change the math.

The science backs this up in the range that matters. You can grind more reps on the squat than the bench at light loads, but that gap shrinks to almost nothing at heavy, low-rep sets (Shimano & Kraemer, 2006) — which is exactly the 3–6 reps we recommend for an accurate estimate. Where the lift genuinely changes things, this tool already adapts: the strength standards are lift-specific (a 315 lb max is strong on the bench but ordinary on the deadlift), the plate-club milestones differ, and the deadlift carries a “treat it as a floor” caveat because rep-based formulas systematically under-predict it (LeSuer 1997). Pick your lift to get the right standards and framing — the headline estimate itself is honestly lift-agnostic.

1RM by lift — bench, squat & deadlift

Each lift has its own dedicated calculator with lift-specific strength standards and framing: the bench press calculator, the squat calculator, and the deadlift calculator (which flags the deadlift’s tendency to be under-predicted). Or pick the lift in the selector above to relabel this tool.

Frequently asked questions

How accurate is a 1RM calculator?
Within about ±3% when your set is in the 2 to 10 rep range, most accurate at 6 reps or fewer, and less reliable above 10 reps (LeSuer 1997; Reynolds 2006). It is an estimate from published formulas, not a measured max.

Which 1RM formula is best — Epley or Brzycki?
At low reps they are very close; Epley reads slightly high and Brzycki slightly low, so this calculator averages them. Wathan is often cited as the single most accurate across bench, squat and deadlift (LeSuer 1997).

How do I calculate my one-rep max without a calculator?
Use the Epley formula: 1RM = weight × (1 + reps ÷ 30). For 225 lb × 5 that is 225 × (1 + 5/30) ≈ 263 lb. Averaging with Brzycki (weight × 36 ÷ (37 − reps)) gives a tighter estimate.

What percentage of my 1RM should I lift for muscle growth?
Hypertrophy work generally sits around 65 to 80 percent of your 1RM for moderate-to-higher reps; strength work is 80 percent and up (ACSM 2026 position stand, load prescription).

Can I estimate my 1RM from high reps like 20?
You can, but accuracy drops sharply above about 10 reps — endurance and fatigue resistance start to matter more than pure strength. Use a set of 3 to 6 reps for a trustworthy number.

Should beginners test their true one-rep max?
Usually not. Beginners are still learning technique, so a true max attempt is higher-risk and less meaningful. Estimate from a submaximal set instead, and re-check as you get stronger.

Why is my 1RM estimate the same for bench, squat and deadlift?
Because the formulas use only weight and reps, not the exercise — so every 1RM calculator returns the same number for the same set. The real per-lift difference is small at the 3–6 reps we recommend (Shimano 2006). The lift matters most for your strength standards and for the deadlift, which is under-predicted (LeSuer 1997) — both of which this tool already handles when you pick a lift.

Related calculators & gear

Jump to the bench press calculator, squat calculator, or deadlift calculator. Train heavy solo with a rack with safety arms, a quality Olympic barbell, and the plates to hit these loads. Planning a build? Grab the free garage gym planner or read how to build a home gym.

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