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One-Rep-Max Calculator | Estimate 1RM and Training Percentages

Enter the weight you lifted and the number of reps you completed, and this 1RM calculator estimates your one-rep max using the Epley and Brzycki formulas, then prints a full training percentage table (55–95%) for programming your next sessions. It also lets you work backwards from a target 1RM to find the loads for each rep range.

Last updated: June 2026 · Free · No sign-up required

Results

Enter values above and click Calculate to see your result instantly.

Quick reference

Training percentages of 1RM:

% of 1RM	Reps	Use
100%	1	Max strength test
90%	~4	Strength
80%	~8	Strength + size
70%	~12	Hypertrophy
60%	~15+	Endurance

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This calculator gives you the same number a clinician would compute by hand from your inputs. It is informational, never a substitute for a doctor. If a result surprises you, write it down and discuss it at your next appointment — that conversation is the goal, not a verdict from a webpage.

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Your weight, height, age, pregnancy details, and any other health input never leave your browser. Calculations run client-side; nothing is logged or stored on our side. We don't want your medical data — we just want the formula to work for you.

Interpretation guide

1RM formulas:

Formula	Equation
Epley	w x (1 + reps/30)
Brzycki	w x 36 / (37 - reps)
Lombardi	w x reps^0.10

lightbulb Worked example

Let's say you are using the One Rep Max Calculator. Enter the weight you lifted and the number of reps you completed, and this 1RM calculator estimates your one-rep max using the Epley and Brzycki formulas, then prints a full training percentage table Enter the values that match your situation into the input fields and press calculate — using realistic numbers makes the result directly useful for you.

Result: The calculator instantly applies the formula Epley 1RM = weight x (1 + reps / 30); best accuracy at <= 10 reps and returns the result with appropriate precision.

What this means: Read the result in the context of what you are measuring. The step-by-step breakdown lets you confirm the math and understand which input most affects the outcome.

Formula & methodology

Formula: Epley 1RM = weight x (1 + reps / 30); best accuracy at <= 10 reps

The One Rep Max Calculator is built on a well-established calculation method. It uses the formula Epley 1RM = weight x (1 + reps / 30); best accuracy at <= 10 reps to turn your inputs into a reliable result. Enter the weight you lifted and the number of reps you completed, and this 1RM calculator estimates your one-rep max using the Epley and Brzycki formulas, then prints a full training percentage table (55–95%) for The steps are shown on the page so you can follow the reasoning from input to output.

Your one-rep max is the most weight you can lift once with good form. Rather than testing it directly (which is risky), the calculator estimates 1RM from a submaximal set using formulas like Epley and Brzycki. Accuracy is best at 10 reps or fewer. From your 1RM you can program training loads — for example sets at 70–85% for muscle growth or 90%+ for peak strength.

What is the One Rep Max Calculator?

The One Rep Max Calculator is a free, browser-based health calculator tool that helps you Enter the weight you lifted and the number of reps you completed, and this 1RM calculator estimates your one-rep max using the Epley and Brzycki formulas, then . Instead of working through the math by hand or in a spreadsheet, you enter your values and the calculator returns an accurate result instantly — while still showing the formula and the steps so you can verify the reasoning. It is designed for quick everyday use: no sign-up, no installation, and everything runs locally in your browser for complete privacy.

How to use the One Rep Max Calculator

Enter the required values into the input fields.
Press the calculate button — the result appears immediately, updated live as you change any value.
Read the step-by-step breakdown below the result to see exactly how the calculation was performed.
Use the interpretation guide to understand what the result means for your situation, and try different inputs to see how they change the outcome.

How to use the One Rep Max Calculator

Enter the weight you lifted and the number of reps you completed, ideally in the 3–10 rep range, and press calculate. The tool applies the Epley formula: 1RM = weight × (1 + reps ÷ 30), which is most accurate at 10 reps or fewer. For example, benching 185 lb for 5 reps estimates a 1RM of about 216 lb. If you know your actual tested max, you can work the formula backward to find the right training weights for any rep count.

Interpreting your result

The estimated 1RM is a planning number, not a number to test blindly — it lets you set training loads as percentages of a true max without risking a heavy single. Most programmes use percentages of 1RM: 65–75% for hypertrophy volume work, 80–90% for strength work, and 90%+ for peaking. Because the Epley estimate becomes less accurate beyond 10 reps, stick to lower-rep sets when you want a reliable number. The calculator also shows the estimated max for several rep ranges so you can adjust loads across your programme.

Common mistakes to avoid

The most common error is testing a true 1RM without a spotter or a proper warm-up — the risk-to-reward ratio is poor, and the estimate from a 3–5 rep set is close enough for programming. Second, using the formula on sets with sloppy form or partial reps, which inflate the estimate. Third, extrapolating beyond 10 reps, where fatigue rather than strength limits the set. Finally, treating the estimated max as fixed — strength changes weekly, so recalculate whenever you hit a new rep record at a given weight.

Tips for best results

Use a weight you can lift for at least 3 clean reps and record the honest rep count. Warm up thoroughly before the working set — the estimate assumes a fresh muscle. Recalculate after each new rep PR: if you press 190 lb for 5, the new estimate is about 222 lb. For programme design, keep your training weights at 70–85% of the estimate for most work. If you are new to lifting, prefer higher-rep work (8–12) and let the estimate guide progression rather than attempting maximal lifts early.

Authoritative source: U.S. Centers for Disease Control and Prevention

Frequently asked questions

How do I estimate my one rep max?

Enter the weight you lifted and the number of reps you completed — ideally a clean set of 3 to 10 reps — and the tool applies the Epley formula: estimated 1RM = weight × (1 + reps ÷ 30). For example, benching 185 lb for 5 reps estimates a 1RM of about 216 lb. The estimate is most reliable at 10 reps or fewer, where strength rather than fatigue limits the set.

How accurate are 1RM estimates?

The Epley formula is one of the best predictors of a true one-rep max, typically landing within 2–5% of the tested value when used in the 3–10 rep range. Accuracy depends on honest reps, fresh muscles, and solid form — sloppy or high-rep sets inflate the estimate. Treat the result as a planning number for setting training loads, not a number to go out and test.

What percentage of 1RM should I train at?

The One Rep Max Calculator is free, private, and accurate: it runs entirely in your browser (no uploads, no accounts), applies the standard calculation, and explains each step so you can verify the result. Enter the weight you lifted and the number of reps you completed, and this 1RM calculator estimates your one-rep max using the Epley and Brzycki formulas, then prints a full training percentage table (55–95%) for programming your next sessions. It also lets There is no limit on usage, and it works on any device.

Should I test my actual 1RM?

Testing a true 1RM is risky without a seasoned spotter and a long warm-up, and the injury-to-information ratio is poor for most lifters. The Epley estimate from a 3–5 rep set is within 2–5% of the true max and plenty accurate for programming. Reserve true 1RM testing for advanced lifters in competition preparation, and even then only with proper setup.

Why do the formulas give slightly different results?

Different 1RM formulas were fitted on different data sets, so they emphasize rep ranges differently: the Epley formula (weight × (1 + reps ÷ 30)) is standard for sets of 10 reps or fewer, while other equations like Brzycki or Lombardi diverge more at higher rep counts. The calculator uses Epley as the default and shows the working, so the result is consistent and traceable.

What does the One Rep Max Calculator do?

Enter the weight you lifted and the number of reps you completed, and this 1RM calculator estimates your one-rep max using the Epley and Brzycki formulas, then prints a full training percentage table (55–95%) for programming your next sessions. It also lets. The calculator takes your inputs, applies the standard calculation, and returns a clear result so you can make an informed decision without doing the math by hand.

What formula does the One Rep Max Calculator use?

It uses the Epley formula: estimated 1RM = weight × (1 + reps ÷ 30). For 185 lb lifted for 5 reps, that is 185 × (1 + 5 ÷ 30) = 185 × 1.167 ≈ 216 lb. The formula is most accurate at 10 reps or fewer, which is why the tool suggests staying in the 3–10 rep range when you enter a set.

Is the One Rep Max Calculator free and private?

Yes — the One Rep Max Calculator. There is no sign-up, no paywall, no trial, and no limit on how many calculations you can run. CalcaTools covers its costs with non-intrusive display advertising, so the calculator itself never asks for payment or restricts any feature.

How accurate is the One Rep Max Calculator?

The Epley estimate typically falls within 2–5% of a tested one-rep max for sets of 3–10 reps, which is precise enough for programming training loads at 65–90% of max. Accuracy drops with higher reps, poor form, or fatigue, and varies slightly by lift. Use it to set weights for your programme, and recalculate whenever you hit a new rep record.

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