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1 Rep Max Calculator — Estimate Your 1RM From Any Set

Type a weight and reps. Get your estimated 1RM and a full rep-percentage table.

Estimated 1 rep max
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Reps Weight % 1RM
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What is 1 rep max calculator?

An estimated 1RM is what most strength programs are actually built around. The math is the Epley formula — 1RM = weight × (1 + reps / 30) — and it works because the relationship between rep count and intensity is roughly linear in the 1–10 rep range that competitive lifting and strength programming live in. Past 10 reps the relationship curves and the formula starts drifting; that’s why this calculator rejects input above 10 reps, and why the rep table caps at 10 rows.

The rep-percentage table below the headline is the training prescription that programs like 5/3/1 and the Texas Method actually call for. Each row is a rep count, the weight you’d load to hit that rep count, and the percent of your 1RM that weight represents. The weights are rounded to the smallest plates you’ll find on a commercial gym floor (5 lb in the US, 2.5 kg elsewhere) so each row is a number you can actually load on the bar. One subtlety: the displayed weight and the percent column are independent roundings, so a row showing “200 lb / 86 %” doesn’t mean the percent is exactly 86% of the headline — it means the weight rounds to 200 and the unrounded percent is between 85.5 and 86.5.

Privacy is the final detail worth naming. Every calculation runs locally in your browser. The weight and reps you type never leave your device — there is no server, no API, no analytics on input values. The only state saved is your unit preference (lb vs kg) in localStorage, so the toggle remembers your choice next visit. The page does carry a third-party display ad slot (which is how the site stays free), but the ad has no access to the calculator’s state.

When to use a 1 rep max calculator

  • Picking a working weight for today's set — You hit 200 lb × 5 reps last week and you want to know what to load for a heavy triple this week. The rep table maps 3 reps directly to a plate-rounded working weight — about 91% of your estimated 1RM, rounded to the nearest 5 lb.
  • Planning a strength program from your e1RM — Programs like 5/3/1 and the Texas Method prescribe percentages of a training max. The rep table is the lookup the program needs — every row is a percentage of your 1RM and the weight that percentage rounds to on the bar.
  • Tracking PR progress over weeks — Testing a true 1RM is fatiguing and injury-risk-elevated, so most lifters track progress through a top set of 3–8 reps and convert to an estimated 1RM. The same rep × weight set tested at week 1 vs week 6 gives an apples-to-apples comparison without ever touching a true single.

How to use the 1 Rep Max Calculator — Estimate Your 1RM From Any Set

  1. Pick your unit — Toggle between lb and kg at the top of the form. Your choice is remembered for next time.
  2. Enter the weight you lifted — Type the weight on the bar. Decimals are accepted (handy for half-kilo plates), and the mobile keyboard opens to a numeric layout automatically.
  3. Enter the reps you completed — Type the number of reps you finished at that weight. The estimate is most accurate at 1–10 reps; past 10 the formula starts to drift, so we cap input there.
  4. Read the estimated 1RM and the rep table — The headline at the top of the result panel is your estimated one-rep max. The 10-row table below it is your training prescription — each row maps a rep count to the working weight (rounded to plate-friendly numbers) and the percent of 1RM that weight represents.

Worked examples

5 reps × 200 lb

Input:  Weight 200 lb, Reps 5
Output: Estimated 1RM ≈ 233.3 lb

A typical heavy-five working set. The rep table shows 200 lb maps to about 86% of 1RM.

8 reps × 60 kg

Input:  Weight 60 kg, Reps 8
Output: Estimated 1RM ≈ 76 kg

An 8-rep hypertrophy-range set. Useful when programming AMRAPs (as-many-reps-as-possible) — the e1RM tracks progress without testing a true single.

3 reps × 315 lb

Input:  Weight 315 lb, Reps 3
Output: Estimated 1RM ≈ 346.5 lb

A heavy triple is one of the most reliable submaximal sets for estimating 1RM — close enough to the true max that the formula has very little drift.

Frequently asked questions

What is a 1 rep max?
Your one-rep max (1RM) is the heaviest weight you can lift one time with correct form on a given exercise. Most lifters never test it directly — testing a true 1RM is fatiguing and elevates injury risk — and instead estimate it from a submaximal set. That estimate is what this calculator computes.
How accurate is the Epley estimate?
Within about ±2–3% of a true 1RM at low rep counts (1–5 reps), drifting wider at higher rep counts (6–10 reps) and becoming unreliable past 10. The estimate is a planning tool, not a medical measurement — day-to-day variance in actual lifting (sleep, food, fatigue) is roughly the same magnitude as the formula's error.
Why does the calculator only accept 1–10 reps?
The Epley formula's published validity range is 1–10 reps. Past 10 reps the formula systematically over-estimates 1RM because it assumes a linear relationship between reps and intensity, and that relationship breaks down once the set crosses into endurance territory. We cap input at 10 to avoid shipping numbers we can't stand behind.
Why does the calculator return my exact weight when I enter 1 rep?
Because that weight is your 1RM by definition — you just lifted it once. The literal Epley formula returns weight × 1.033 for a 1-rep set, which contradicts the input ('I lifted 200 × 1, so my 1RM is 207'). Every reputable 1RM calculator overrides this case to return the input weight unchanged, and that's what we do here.
What's the difference between Epley, Brzycki, and other 1RM formulas?
Several published formulas exist (Epley, Brzycki, Lombardi, Wathan, O'Conner). At low rep counts (1–5) they agree within about 2%; at higher rep counts they diverge by up to 10–15%. Epley is the most widely taught — most strength textbooks use it, and most online calculators land on it. We use Epley exclusively here for consistency. If you want to compare estimates, lift a 5-rep set and check Epley vs Brzycki by hand: 200 × (1 + 5/30) = 233.3 vs 200 × 36 / (37 − 5) = 225 — about a 4% spread.
Should I actually test my true 1RM in the gym?
Rarely, and only with experience. A true 1RM is a maximal singles attempt — high CNS fatigue, real injury risk if form breaks under load, and a single failed attempt can wreck the session. Most strength programs explicitly avoid testing 1RMs, prescribing percentages of an estimated 1RM (called a training max, often set at 90–95% of estimated 1RM) instead. If you do test, do it under spotters or with safety bars, after a thorough warm-up, and only on lifts you've trained for years.
Why are the table weights rounded to 5 lb / 2.5 kg?
Those are the smallest plates you'll typically find on a commercial gym floor. Rounding to plate-friendly numbers means each table row is a weight you can actually load on the bar without fractional plates. The headline 1RM stays unrounded (one decimal) because it's an estimate, not a weight you'll load — over-rounding the estimate would obscure small week-to-week changes in your tracking.
Does this work for any lift (squat, bench, deadlift, OHP)?
Yes. The Epley formula is lift-agnostic — it relates rep counts to intensity in general, not to any specific lift. The same calculator works for squat, bench press, deadlift, overhead press, row, weighted pull-up, and any other compound or isolation exercise where you can count reps. The relative accuracy varies slightly by lift (deadlift e1RMs tend to read a bit high because deadlifts fatigue the CNS faster), but the formula itself is the same.
Are my numbers stored or sent anywhere?
No. Every calculation runs locally in your browser. Your weight and reps are never transmitted — there is no server, no API call, no analytics on input values. The only state we save is your unit preference (lb vs kg) in localStorage, so the toggle remembers your choice next visit. The page does carry a third-party display ad slot (which is how the site stays free), but the ad has no access to the calculator state.

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