One Rep Max Calculator
Estimate your 1RM from a set and reps.
Results update as you type.
How it works
Your one rep max is the heaviest weight you can lift for a single repetition of an exercise, and this one rep max calculator estimates it from a set you have already completed without you ever attempting a risky maximal lift. Enter the weight you moved and the number of clean reps you finished, and it applies the Epley formula to project your 1RM, then works out your 90% and 80% loads for programming heavy and moderate training days. Knowing your one rep max matters because most strength programs prescribe weights as a percentage of it. Powerlifters, athletes, and everyday lifters use the number to set training intensity, track progress over weeks, and compare lifts fairly across bodyweights. Testing a true max is fatiguing and carries injury risk, so an estimate from a submaximal set is safer and can be repeated often. The formula works because the reps you can complete at a load are strongly related to the single maximum you could handle, and Epley captures that relationship with a simple linear adjustment. Coaches, personal trainers, and gym-goers rely on a one rep max calculator to program squats, bench presses, and deadlifts with confidence.
1RM = weight × (1 + reps ÷ 30)
The Epley formula estimates your one rep max by scaling the weight you lifted up in proportion to how many reps you managed. Each additional rep adds roughly one-thirtieth of the lifted weight, because completing more reps at a given load implies a higher true maximum. Dividing reps by 30 and adding one gives the multiplier applied to the weight to project a single all-out lift.
Source:Epley 1985 (one-rep max)
We review all our tools from time to time to ensure accuracy.
Worked example
How to use this calculator
- 1
Enter your values
Enter weight lifted and reps completed.
- 2
Adjust the options
Fine-tune any options to match your situation.
- 3
Read your result
One rep max updates instantly as you type — no button to press.
Frequently asked questions
How accurate is an estimated one rep max?
Estimates are most accurate when the rep count stays low, roughly under ten, because the relationship between reps and maximum strength is close to linear in that range. Above ten reps, endurance and technique start to influence the result, so the projection drifts. Use a set of three to eight solid reps for the most reliable figure, and re-test periodically as your strength changes over time.
What is the Epley formula?
The Epley formula estimates one rep max as the weight lifted multiplied by one plus the reps divided by thirty. Published by Boyd Epley in 1985, it is one of the most widely used strength equations because it is simple and reasonably accurate for moderate rep ranges. Several alternative formulas exist, such as Brzycki, and they give slightly different numbers, but Epley remains a trusted standard for gym programming.
Why does the calculator show 90% and 80% loads?
Strength programs usually prescribe working weights as a percentage of your one rep max rather than the max itself. Showing your 90% and 80% loads lets you translate the estimate directly into training numbers: roughly 90% for heavy triples and 80% for higher-volume sets. This saves you the arithmetic and helps you pick weights that match the intensity your program calls for on any given day.
Should I actually attempt my one rep max?
Attempting a true one rep max is demanding and carries a higher injury risk, especially without a spotter and proper warm-up. For most lifters, estimating from a submaximal set is safer and gives a number precise enough for programming. Competitive powerlifters do test real maxes under controlled conditions, but for general training an estimate lets you track progress frequently without the fatigue and risk of maximal attempts.
Does one rep max differ between exercises?
Yes. Your one rep max is specific to each lift because different exercises recruit different muscles and leverages. A deadlift max is typically higher than a squat max, which is higher than a bench press max, for most people. Estimate each lift separately using a set performed on that exercise, and avoid applying a squat percentage to your bench press, since the ratios vary by individual and movement.