About the One Rep Max Calculator
One Rep Max Calculator estimates the heaviest weight you could lift once (your 1RM) from a lighter set of several reps, so that you do not have to attempt a risky maximum lift. Enter the weight you lifted and how many reps you completed, choose kilograms or pounds, and the tool gives an estimate using the average of seven well-known formulas (Epley, Brzycki, Lander, Lombardi, O'Conner, Mayhew and Wathan), or the single formula you pick. It also shows a chart of training weights from 100 down to 50 percent of your max, with the number of reps each is roughly good for, and lets you round the weights to the plates you have. It works for the bench press, squat, deadlift, overhead press and other lifts. The result is an estimate: actual maximums vary with the lift, your experience and the day.
Updated September 2026
How to use the One Rep Max Calculator
- 1Choose kilograms or pounds.
- 2Enter the weight you lifted and the number of reps you completed with good form.
- 3Choose a formula, or leave it on the average of all seven.
- 4Choose the rounding that matches your plates.
- 5Read your estimated 1RM and the percentage chart for training weights.
Why estimate rather than test
Lifting a true maximum takes a lot out of the body and the nervous system, and it can lead to injury if the form slips. Estimating from a set of three to eight reps gives a usable number with much less risk and fatigue. Many coaches use the estimate to set the weights for the weeks ahead and test a true max only rarely.
You can also use estimated maxes to compare sessions: if you did 60 kg for 10 reps last month and 65 kg for 10 reps now, your estimated max has risen by about 8 percent.
Getting an accurate estimate
- Use a set taken close to failure, with good form and a full range of motion.
- Choose a set of 3 to 8 reps: fewer is near a real max, more depends on endurance.
- Use the same exercise, bar and technique each time, such as the same bench pause.
- Count only clean reps, not reps with help from a spotter or bouncing.
- Compare results from the same formula over time, since the trend is what matters.
Turning the max into a programme
Strength work is often done at 80 to 90 percent of the 1RM for 2 to 6 reps, muscle building at about 65 to 80 percent for 6 to 12 reps, and endurance work at lower percentages and higher reps. The chart shows the weights for each step, and the rounding option puts them on the plates you have, for example 2.5 kg jumps or 5 lb jumps.
Beginners often gain fast and should re-estimate every few weeks so their percentages keep up with their progress.
Limits and related tools
These formulas were made from data on average lifters and certain exercises, so they can over- or underestimate for you, especially in lifts such as the deadlift or the squat where technique varies. Use them as a guide, not a rule. This tool is general information, not medical advice.
To plan meals around training, Macro Calculator and Calorie Calculator give daily targets, Target Heart Rate Calculator helps with cardio zones, and Ideal Weight Calculator and Body Fat Calculator track body composition.
Features
- Seven formulas plus their average
- Kilograms and pounds
- Percentage chart from 100 to 50 percent
- Approximate reps for each percentage
- Rounding to your plate size
- Works for any lift
- Runs in your browser
Frequently asked questions
What is a one rep max?
Your one rep max, or 1RM, is the most weight you can lift for a single repetition of an exercise with proper form. Lifters use it to set training loads as a percentage of that maximum, and to track strength over time.
How is a 1RM estimated from several reps?
Formulas built from studies of lifters relate the weight and reps of a submaximal set to the max. The Epley formula is 1RM = weight × (1 + reps ÷ 30), so 80 kg for 8 reps gives about 101 kg. The Brzycki formula is weight × 36 ÷ (37 − reps), which gives about 99 kg for the same set.
Which formula is the most accurate?
None is best for everyone. They agree closely for sets of two to ten reps and drift apart with higher reps. Using the average of several is a sensible way to smooth out their differences, and it is the default here. Estimates from sets of 10 or fewer reps are the most reliable.
Why should I avoid very high reps?
The more reps in the set, the more the estimate depends on fatigue, breathing and endurance rather than pure strength, and the less accurate it becomes. The tool accepts up to 30 reps, but treat estimates from more than 10 as rough.
How do I use the percentage chart?
Programmes often prescribe work as a percentage of the 1RM, for example 5 sets of 5 at 80 percent. Read the weight for that percentage from the chart. The reps column shows roughly how many repetitions are possible at that load for an average lifter, and yours may differ.
Is it safe to test a real one rep max?
A true max attempt carries more risk than a normal set, especially without a spotter or safety bars. An estimate from a controlled set of several reps is a safer way to know your level. If you do test, warm up properly, use spotters and stop if your form breaks down.