One Rep Max (1RM) Calculator

Your one-rep max (1RM) is the most weight you can lift for a single rep. It’s the number most strength programs are built around, so once you know it (or a close estimate), the weight on every working set becomes simple math.

You don’t have to grind out a true max to find it. Enter a weight you’ve lifted, the reps you got, and your RPE if you tracked it. The calculator estimates your 1RM and fills in your working weights at every percentage. Below the tool, I’ll walk through how to read those numbers and actually use them.

What Is a One-Rep Max?

A one-rep max is the heaviest weight you can lift one time with good form. Powerlifters test it on the platform. Most everyone else estimates it, because maxing out every few weeks beats you up and isn’t needed to train hard.

A few terms get thrown around, so here’s how I use them.

• 1RM is a true, tested single. You actually lifted it.
• e1RM is an estimated 1RM, calculated from a set you did for multiple reps. That’s what this tool gives you.
• PR is a personal record at any rep count, like a 5-rep PR or a 3-rep PR.

Why your 1RM matters

Most good programs assign weight as a percentage of your max. 5/3/1 works off 90% of it. Sheiko prescribes nearly everything in percentages. Even if you train mostly by feel, knowing your estimated max tells you whether that heavy top set was a comfortable 80% or a grinding 95%.

How This Calculator Estimates Your Max

The tool runs two of the most-used formulas and averages them.

• Epley: 1RM = weight × (1 + reps / 30)
• Brzycki: 1RM = weight × 36 / (37 − reps)

They agree almost exactly at low reps and spread apart as the reps climb. Averaging them splits the difference. Other formulas exist (Lombardi, Mayhew, Wathan, O’Conner), and they all land in a similar range for sets of five or fewer, which is why the exact formula matters less than most people think.

How accurate is it?

For a set of two to five reps, a good estimate usually lands within a few percent of a tested max. Past about ten reps it gets shaky, because the number of reps you can grind out at a given weight depends heavily on the person and the lift. If you want the closest estimate, use a set of five reps or fewer. A set of three that you took close to failure is about as good as it gets.

The Percentage Chart Is a Starting Point

The tool fills in your weight at every percentage of your estimated max, from 100% down to 50%, with a rough rep count next to each. Treat that chart as a place to start, then let the bar tell you the rest.

Greg Nuckols pulled the data on how many reps people actually hit at a given percentage, and the spread is wide. Two lifters with the same 1RM can get very different reps at 80%. It’s also lift-specific. Most people get more reps at a given percentage on squats than on bench, and more still on higher-rep machine work. Load the weight the chart suggests, see how it moves, and adjust from there.

How to Turn Percentages Into a Program

A percentage is only useful once it’s a real weight on a real day. Say your estimated squat max is 140 kg and your program calls for 5 sets of 5 at 75%. That’s 105 kg per set. Load it, run it, and bump it next week if it moved well.

If you’re not on a set program yet, plug your max into one of these free spreadsheets. They handle the percentage math for you.

• 5/3/1 builds every cycle off 90% of your max (Wendler calls it your training max).
• nSuns auto-calculates every load from your training max and adjusts it week to week.
• GZCLP is a great linear-progression starting point that ties back to your top-set max.
• Madcow 5×5 ramps your weekly sets up to a top set based on your 5-rep max.
• Candito 6 Week uses your max to drive a full peaking block.

RPE and Percentages

RPE (rate of perceived exertion) rates how hard a set felt on a 1 to 10 scale. RPE 10 means nothing left in the tank, RPE 9 means about one rep in reserve, and RPE 8 means roughly two. If you enter an RPE in the calculator, it estimates your max from an RPE chart instead of the rep formulas.

Percentages and RPE answer different questions. A percentage tells you what to load before you walk up to the bar. RPE tells you how to adjust once you’re under it, on a day when you’re strong or a day when you’re beat up. Plenty of lifters use both: percentages to plan the week, RPE to autoregulate each session. If you want to go deeper on this, the RPE calculator breaks down the full chart.

How to Test a True 1RM Safely

If you do want a tested single, work up to it in small jumps with full rest between attempts. A ramp like this gets most people there.

• Empty bar for a few reps, then 40% × 5
• 60% × 3
• 75% × 2
• 85% × 1
• 92% × 1
• Then take your opener and go up in small jumps to a top single

Use a spotter or safety pins on the squat and bench. Rest three to five minutes between the heavy singles so you’re fresh. Skip the max attempt if you’re underslept, sick, or coming back from a layoff, and don’t test more than every few weeks. For most training, an estimate off a hard set of three is all you need.

How to Increase Your 1RM

Your max goes up when you train the lift often, add weight or reps over time, eat enough, and sleep. Progressive overload does the heavy lifting here, and a structured program keeps you honest about it. Pick one of the spreadsheets above, run it for a full cycle, and re-check your estimate with this calculator when you’re done. A little patience goes a long way.

Frequently Asked Questions

How accurate is a one-rep max calculator?

For sets of two to five reps it’s usually within a few percent of your true max. Accuracy drops as the reps go up, so a 3-rep set gives a much better estimate than a 15-rep set.

How many reps should I use for the best estimate?

Five or fewer, taken close to failure. The closer your set is to a true single, the closer the estimate. A set you stopped four reps short will lowball your max.

Which 1RM formula is most accurate?

No single one wins across the board. Brzycki reads a touch lower and Epley a touch higher at moderate reps, and they converge at low reps. This tool averages the two so you don’t have to pick.

What percentage of my 1RM should I lift?

It depends on the goal. Strength work usually lives around 80 to 95%. Hypertrophy work sits closer to 65 to 80% for higher reps. Power and speed work often use 50 to 70% moved fast. The chart in the tool gives you the weight for each.

How does RPE convert to a percentage of my 1RM?

An RPE chart maps how hard a set felt to a rough percentage, based on how many reps you had left. Enter your RPE in the tool and it does the conversion. The RPE calculator shows the full table.

Do I need to test a true 1RM?

Almost never, unless you compete in powerlifting. A solid estimate off a heavy set of three gives you everything you need to run a percentage-based program without the fatigue and risk of a real max attempt.

How often should I re-check my max?

Every training cycle, or every four to eight weeks, is plenty. Re-run this calculator off a heavy set at the end of a block to see where you stand and set your next round of percentages.

Why can I do more reps at a given percentage on squats than on bench?

Bigger lifts that use more muscle, like the squat and deadlift, tend to give you more reps at the same percentage than the bench press. It’s one reason a single percentage chart can’t be exact for every lift. Use it as a guide and adjust per lift.

Download the Spreadsheet Version

Prefer a sheet you can save? The original 1RM calculator spreadsheet is still available.

Open the 1RM calculator spreadsheet and make a copy to use it.

About Kyle Risley

Kyle Risley founded Lift Vault in 2016 to make finding great powerlifting programs easier. Since then, the site has grown to include hundreds of programs for strength, bodybuilding, Olympic weightlifting, and more. He currently lives in Massachusetts and continues to compete in powerlifting.