One Rep Max Calculator

How to use this calculator

1. Enter the weight you lifted. Use the weight from a hard set you actually completed — a set where you stopped within a rep or two of failure. Toggle between pounds and kilograms; the number converts automatically.
2. Enter the reps you got. Any number from 1 to 15. The estimate is most accurate in the 2–10 rep range; above 12 reps the formulas start to disagree and the number gets less reliable (the tool tells you when you're there).
3. Pick the lift — bench, squat, deadlift, overhead press, or barbell row. This just labels your result and your saved log; the math is identical for every lift.
4. Read your estimated 1RM — the big number is the average of all seven formulas, and the smaller "range across 7 formulas" shows you how much they disagree.
5. Use the training-percentage chart below it to program your sets — it converts your 1RM into working weights at every intensity from 50% to 100%, with the rep target and training focus for each.
6. Save your max to track progress over time, and export a clean PDF to bring to a coach or keep in your training journal. Everything stays on your device.

Why this 1RM calculator is different

Most one-rep-max calculators online run a single formula, print one number, and route you toward a supplement brand. The problem is that no single formula is right for everyone — they were each fit to different lifters and rep ranges, and they can disagree by 15–20 pounds on the same set. Here's what this tool does differently:

• Seven formulas, averaged. It runs Epley, Brzycki, Lombardi, O'Conner, Wathan, Mayhew, and Lander all at once and reports the average — which is more robust than trusting any one equation. Averaging multiple prediction equations is the standard way to reduce the error of any single model.
• The spread is shown, not hidden. You see the lowest and highest of the seven estimates side by side, so you know whether the formulas agree (a tight range = a confident estimate) or disagree (a wide range = treat it as a ballpark). No other consumer 1RM tool surfaces this.
• A full working-weight chart. Your 1RM is only useful if you can program with it. The percentage table turns it into real barbell weights at 50–100%, rounded to the nearest 5 lb (or 2.5 kg) so you can actually load the bar, with the rep target and training focus for each intensity.
• Every formula is printed with its equation. You can see exactly how each estimate is produced and which formulas are known to read high or low — full methodology, not a black box.
• Save, share, and export. Track your maxes across every lift over time, share a link with your exact numbers, and export a branded PDF. Everything runs on your device — nothing is uploaded.
• Reviewed by a physician. Most 1RM widgets are anonymous. This one is reviewed by Dr. David Taylor, MD, PhD, and framed with the safety context heavy lifting actually deserves.

How this calculator works (the seven formulas)

A one-rep max estimate predicts the most weight you could lift once from a set you did for more than one rep. Every formula takes your weight (w) and reps (r) and returns an estimated 1RM. This tool computes all seven and averages them:

• Epley: 1RM = w × (1 + r / 30) — the most widely used; solid through moderate rep ranges.
• Brzycki: 1RM = w × 36 / (37 − r) — popular for low reps (2–5); tends to read low at high reps.
• Lombardi: 1RM = w × r0.10 — a power-curve fit that stays gentle across the range.
• O'Conner: 1RM = w × (1 + 0.025 × r) — a simple, conservative linear estimate.
• Wathan: 1RM = 100w / (48.8 + 53.8 × e−0.075r) — an exponential fit validated on trained lifters.
• Mayhew: 1RM = 100w / (52.2 + 41.9 × e−0.055r) — exponential; reads slightly high at high reps.
• Lander: 1RM = 100w / (101.3 − 2.67123 × r) — also called McGlothin; linear in reps.

At exactly one rep, the weight you lifted is your one-rep max, so the tool returns it unchanged. The formulas all converge near 1 rep and gradually fan out as reps climb — which is exactly why a set of 3–5 gives a tighter, more trustworthy estimate than a set of 15.

The training-percentage chart: turning your 1RM into working weights

Knowing your max is only step one — strength programs are written in percentages of your 1RM. A 5×5 strength block might call for 85%; a hypertrophy day might live at 70–75%; a heavy single sits at 95%+. The chart in the calculator does that math for you, converting your estimated max into the actual weight to put on the bar at every intensity, alongside the rough number of reps most people can do there and what that zone trains:

• 90–100% — max strength. 1–4 reps. Neural, heavy, low volume. This is where powerlifters live in peaking blocks.
• 80–90% — strength. 4–6 reps. The bread-and-butter of getting stronger without maxing out every session.
• 70–80% — hypertrophy. 6–12 reps. The classic muscle-building range; enough load, enough volume.
• 60–70% and below — endurance, volume, and warm-ups. Higher reps, lighter load, more metabolic and technique work.

Weights are rounded to the nearest 5 lb (or 2.5 kg) so they map to real plates. If you're building strength at home rather than in a gym, our resistance-band guide covers how to add and vary load for accessory work when a full rack isn't available.

Three worked examples

A 225 lb bench for 5 reps

The classic gym benchmark. Enter 225 lb × 5 and the seven formulas land between about 253 and 268 lb, averaging an estimated 260 lb bench 1RM. To train it, the chart puts your 85% strength work around 220 lb and your 70% hypertrophy sets near 180 lb.

A 100 kg squat for 3 reps

A triple is a great estimator because the formulas agree closely at low reps. 100 kg × 3 gives a tight spread and an estimated 109 kg squat max — so a 90% heavy single would be loaded near 97.5 kg and a 75% volume day around 82.5 kg.

A 135 lb overhead press for 10 reps

Higher reps mean a wider spread — here the formulas range from roughly 169 to 182 lb, averaging about 177 lb. That gap is the honest signal that a 10-rep estimate is a ballpark; if you want a number you can program tightly around, retest with a heavier set of 3–5. Consistent overhead work is demanding on the shoulders, which is one reason a collagen supplement is popular with lifters looking after their connective tissue.

Frequently asked questions

How accurate is a one-rep max calculator?

For sets in the 2–10 rep range performed close to failure, a good multi-formula estimate is usually within about 5–10% of a true tested max — plenty accurate for programming your training. Accuracy drops as reps climb (a set of 15 involves more conditioning and pacing than pure strength) and depends on how close you stopped to failure. That's why this tool averages seven formulas and shows you the spread rather than pretending a single number is exact.

Which 1RM formula is the best?

There's no single winner — Brzycki and Epley are the most popular and tend to agree well at low reps, while exponential fits like Wathan and Mayhew hold up a little better at higher reps. Because each was derived from a different group of lifters, the most reliable approach for a general audience is to average several, which is exactly what this calculator does.

How do I test my one-rep max safely?

Warm up thoroughly with progressively heavier singles, always use a spotter (or safety pins/arms in a rack), and never chase a grinding max rep with bad form. For most people, estimating a 1RM from a set of 3–5 is safer and nearly as useful as actually testing one — you get the number without the injury risk of a true limit attempt.

What percentage of my 1RM should I train at?

It depends on your goal: roughly 85–95% for maximal strength (low reps), 70–85% for a mix of strength and muscle, and 65–75% for hypertrophy and higher-volume work. The percentage chart in this tool shows the exact weight for each intensity so you can build your sets directly from your estimated max.

Can I use this for dumbbell or machine lifts?

Yes — the formulas only need weight and reps, so they work for any exercise, including dumbbell, machine, and cable movements. Just remember that for dumbbell lifts you typically enter the weight of each dumbbell as your training programs expect, and that stability-limited or machine lifts can estimate slightly differently than a barbell.

Can I embed this calculator on my own site?

Yes — copy the embed snippet at the bottom of this page. The embedded version is a streamlined widget for coaches, gyms, and training blogs, with required attribution built in. There's no fee, no signup, and no analytics attached.

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• Lean Body Mass Calculator — Boer, James, and Hume formulas plus a protein target based on your lean mass.
• Protein Intake Calculator — how many grams of protein you need to build muscle, with five evidence-cited goals.
• TDEE Calculator — daily calorie needs from three formulas, with a goal-based calorie and macro table.
• Fat-Burning Heart Rate Calculator — your training zones by age with four formulas side-by-side.
• Browse all free tools by Dr. Taylor →

Dr. Taylor's recommendations for lifters

Progress on the big lifts is built on recovery — protein to rebuild, connective-tissue support for joints under load, and controlling the inflammation and training stress that heavy work creates. Each links to the full review with current top picks, prices, and honest pros and cons:

• Best Collagen Supplements — connective-tissue protein that lifters use to support tendons, ligaments, and joints under heavy load.
• Best Ashwagandha Supplements — studied for strength gains, recovery, and managing the cortisol response to hard training.
• Best Turmeric & Curcumin Supplements — researched for exercise-induced inflammation and post-training joint soreness.

Getting enough total protein is the foundation under all of it — see our protein powder guide and the protein intake calculator to set your daily target.

Sources & methodology

• Epley B. Poundage Chart. Boyd Epley Workout, University of Nebraska, 1985 — the Epley equation.
• Brzycki M. Strength testing — predicting a one-rep max from reps to fatigue. JOPERD 1993;64(1):88–90 — the Brzycki equation.
• Lombardi VP. Beginning Weight Training. Wm. C. Brown, 1989 — the Lombardi equation.
• Wathan D. Load assignment. In: Baechle TR, ed. Essentials of Strength Training and Conditioning. NSCA / Human Kinetics, 1994 — the Wathan equation.
• Mayhew JL, Ball TE, Arnold MD, Bowen JC. Relative muscular endurance performance as a predictor of bench press strength. J Appl Sport Sci Res 1992;6(4):200–206 — the Mayhew equation.
• O'Conner B, Simmons J, O'Shea P. Weight Training Today. West Publishing, 1989 — the O'Conner equation.
• Landers J (McGlothin). Maximums based on reps. NSCA Journal 1985;6:60–61 — the Lander / McGlothin equation.
• Baechle TR, Earle RW, eds. Essentials of Strength Training and Conditioning (NSCA). Human Kinetics — the rep-max percentage relationship behind the working-weight chart.

This tool is reviewed annually for citation currency. About Dr. Taylor · Last reviewed August 6, 2026.

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Free for strength coaches, personal trainers, gyms, and training blogs. Required attribution is included in the snippet. No fee, no signup, no analytics attached to the embed.

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