1RM Calculator
Calculate your One-Rep Max (1RM) – the maximum weight you can lift for one repetition.
Knowing your one-rep max (1RM) can be useful for planning strength workouts, comparing progress, and choosing appropriate training weights. Your one-rep max is the maximum amount of weight you could theoretically lift for a single repetition of a particular exercise.
Testing a true one-repetition maximum can be physically demanding, especially with heavy compound exercises. An easier approach is to estimate your 1RM from a weight you can already lift for several repetitions.
This 1RM Calculator lets you enter the weight you lifted, the number of repetitions you completed, your preferred weight unit, and the formula you want to use. The calculator then estimates your one-rep max and automatically calculates several percentages of that estimated maximum.
The results include:
- Estimated 1RM
- 90% of 1RM
- 85% of 1RM
- 80% of 1RM
- 75% of 1RM
- 70% of 1RM
These percentages can help you turn an estimated maximum into practical training weights for different workout intensities.
What Is a 1RM?
1RM, short for one-repetition maximum, is the maximum weight a person can theoretically lift for one complete repetition of a specific exercise.
For example, if your estimated bench press 1RM is 100 kg, then 100 kg represents your estimated maximum single repetition.
Your 1RM is exercise-specific. Your bench press 1RM will not be the same as your squat 1RM or deadlift 1RM.
A 1RM can be determined through an actual maximum-effort test, but it can also be estimated mathematically from a submaximal set.
For example, if you successfully lift 80 kg for 5 repetitions, a 1RM formula can use those numbers to estimate how much you might be able to lift for one repetition.
Why Calculate Your 1RM?
An estimated one-rep max can be useful for several reasons.
Workout Planning
Many strength programs prescribe training intensity as a percentage of 1RM.
Instead of simply saying “lift a heavy weight,” a program might use 80% of your estimated 1RM.
If your estimated 1RM is 100 kg, then 80% is:
100 × 0.80 = 80 kg
This gives you a practical starting point for selecting your training weight.
Tracking Strength Progress
Your estimated 1RM can also provide a way to monitor progress without regularly performing maximum-effort lifts.
Suppose you previously lifted 70 kg for 8 repetitions and later lifted 75 kg for 8 repetitions. An estimated 1RM calculation can show how your theoretical maximum has changed.
Choosing Training Intensities
Different percentages can be used for different training purposes.
The calculator automatically provides 70%, 75%, 80%, 85%, and 90% of your estimated 1RM, allowing you to quickly compare possible training loads.
How to Use the 1RM Calculator
Using this calculator is straightforward.
Step 1: Enter the Weight You Lifted
Enter the amount of weight you successfully lifted during your set.
For example:
80
Make sure the number represents the weight used for the exercise you are calculating.
The calculator accepts positive weight values and allows decimal values such as 80.5.
Step 2: Choose Your Weight Unit
Select either:
- Pounds (lbs)
- Kilograms (kg)
The calculator does not convert pounds to kilograms or kilograms to pounds. Instead, it performs the calculation using whichever unit you select and displays the result in that same unit.
For example, if you enter 100 kg, the calculated 1RM will be displayed in kilograms.
Step 3: Enter Your Repetitions
Enter the number of repetitions you completed with the selected weight.
The calculator accepts between 1 and 20 repetitions.
For example:
80 kg × 5 reps
means that you lifted 80 kg for five repetitions.
Step 4: Select a Formula
The calculator provides five formula options:
- Epley Formula
- Brzycki Formula
- Lander Formula
- Lombardi Formula
- Average of All
Each formula estimates 1RM using a slightly different mathematical approach.
Step 5: Click Calculate
Select Calculate to generate your estimated 1RM.
The calculator will display the estimated maximum along with several percentage-based training weights.
1RM Calculator Example
Suppose you perform a set of:
80 kg × 5 repetitions
Using the Epley Formula, the calculation is:
1RM = Weight × (1 + Reps ÷ 30)
Substituting the values:
1RM = 80 × (1 + 5 ÷ 30)
This produces an estimated 1RM of approximately:
93.3 kg
The calculator then calculates different percentages of that value.
90% of 1RM
93.3 × 0.90 = 84.0 kg
85% of 1RM
93.3 × 0.85 = 79.3 kg
80% of 1RM
93.3 × 0.80 = 74.6 kg
75% of 1RM
93.3 × 0.75 = 70.0 kg
70% of 1RM
93.3 × 0.70 = 65.3 kg
The calculator displays these results to one decimal place.
The Epley 1RM Formula
The Epley formula is one of the formulas included in the calculator.
Its equation is:
1RM = Weight × (1 + Reps ÷ 30)
For example, if you lift 100 pounds for 5 repetitions:
1RM = 100 × (1 + 5 ÷ 30)
The estimated 1RM is approximately:
116.7 pounds
The Epley formula is particularly straightforward, which makes it easy to understand and use.
The Brzycki 1RM Formula
The Brzycki formula is another method included in the calculator.
The formula used by the tool is:
1RM = Weight × 36 ÷ (37 − Reps)
For example, if you lift 100 pounds for 5 repetitions:
1RM = 100 × 36 ÷ (37 − 5)
The result is approximately:
112.5 pounds
Because the Brzycki formula uses a different mathematical relationship between weight and repetitions, it can produce a different result from the Epley formula.
The Lander 1RM Formula
The calculator also includes the Lander formula.
The equation used is:
1RM = (100 × Weight) ÷ (101.3 − 2.67123 × Reps)
Using 100 pounds for 5 repetitions gives an estimated 1RM of approximately:
112.7 pounds
Like the other formulas, this is an estimate rather than a direct measurement of maximum strength.
The Lombardi 1RM Formula
The Lombardi formula uses a different mathematical approach:
1RM = Weight × Reps^0.10
For example, if you lift 100 pounds for 5 repetitions:
1RM = 100 × 5^0.10
This produces an estimated 1RM of approximately:
117.4 pounds
The Lombardi formula can therefore produce a different estimate from the other formulas using the same weight and repetition count.
What Does “Average of All” Mean?
The calculator includes an Average of All option.
When selected, it calculates an estimated 1RM using all four formulas:
- Epley
- Brzycki
- Lander
- Lombardi
It then calculates the arithmetic average of those four results.
For example, suppose the four formulas produce:
- Epley: 116.7
- Brzycki: 112.5
- Lander: 112.7
- Lombardi: 117.4
The calculator adds these values and divides by four.
This produces a combined estimate of approximately:
114.8 pounds
The average option can be useful when you want to see a blended estimate rather than selecting only one formula.
What Happens When You Enter 1 Rep?
If you enter 1 repetition, the calculator does not estimate your 1RM using one of the formulas.
Instead, it treats the weight you entered as your 1RM.
For example:
100 kg × 1 rep
produces:
1RM = 100 kg
The percentage values are then calculated from that 100 kg value.
This is appropriate because the weight you successfully lifted for one repetition is already a direct single-repetition result.
Understanding 90% of Your 1RM
The calculator shows 90% of your estimated 1RM.
For example, if your 1 appropriate number of repetitions at any percentage varies betweenRM is 200 pounds:
200 × 0.90 = 180 pounds
So 90% of your 1RM is:
180 pounds
This represents a relatively high percentage of your estimated maximum and may be useful when planning heavier training sessions.
The appropriate number of repetitions at any percentage varies between individuals and exercises, so the percentage should not automatically be treated as a guaranteed repetition target.
Understanding 85% of Your 1RM
The calculator also provides 85% of your estimated maximum.
If your 1RM is 200 pounds:
200 × 0.85 = 170 pounds
Therefore:
85% 1RM = 170 pounds
This gives you another reference point between moderate and high training intensity.
Understanding 80% of Your 1RM
At 80%:
200 × 0.80 = 160 pounds
So someone with a 200-pound estimated 1RM would have an 80% training weight of:
160 pounds
This percentage is commonly useful when creating structured strength-training sessions.
Understanding 75% of Your 1RM
At 75%:
200 × 0.75 = 150 pounds
Therefore:
75% 1RM = 150 pounds
This provides a lower training intensity than 80%, 85%, or 90%.
Understanding 70% of Your 1RM
At 70%:
200 × 0.70 = 140 pounds
Therefore:
70% 1RM = 140 pounds
The calculator gives you this percentage automatically so you can compare several possible training weights without performing separate calculations.
Pounds vs. Kilograms
The calculator supports both pounds and kilograms.
If you train using pounds, select:
Pounds (lbs)
If you train using kilograms, select:
Kilograms (kg)
It is important to keep your input and output unit consistent.
For example, if you enter 100 kg, the calculator will estimate your 1RM in kilograms.
If you enter 225 pounds, the result will be displayed in pounds.
The calculator does not automatically convert between the two units.
How Accurate Is an Estimated 1RM?
An estimated 1RM is not necessarily identical to your actual maximum.
Several factors can affect how closely an equation predicts your real one-repetition performance.
These include:
- The exercise being performed
- Your training experience
- Number of repetitions
- Technique
- Fatigue
- Rest between sets
- Range of motion
- Individual strength characteristics
- How close the set was to muscular failure
For this reason, the calculator should be viewed as a planning and estimation tool rather than a guarantee of your maximum lifting ability.
Why Different Formulas Give Different Results
There is no single mathematical formula that will produce exactly the same estimate for every lifter and every repetition range.
The formulas included in this calculator use different equations.
As a result, entering the same weight and repetitions into the Epley, Brzycki, Lander, and Lombardi formulas can produce different 1RM estimates.
For example, one formula might estimate a 1RM of 115 pounds while another estimates 118 pounds.
That difference does not necessarily mean one calculation is incorrect. It reflects the fact that they use different mathematical models.
Choosing a Formula
The calculator allows you to compare several commonly used estimation approaches.
If you prefer a simple calculation, the Epley formula is straightforward.
If you want to compare different equations, the Average of All option combines the results of the four formulas included in the tool.
The most appropriate formula can vary depending on the exercise, repetition range, and individual lifter. It is therefore useful to treat these formulas as estimates rather than absolute measurements.
How to Use 1RM Percentages in Training
Once you know your estimated 1RM, the percentage values can help you organize training loads.
For example, suppose your estimated 1RM is 100 kg.
Your calculator results would be:
- 90% = 90 kg
- 85% = 85 kg
- 80% = 80 kg
- 75% = 75 kg
- 70% = 70 kg
You can use these numbers as reference points when following a workout plan based on percentages.
However, the exact weight you should use for a workout depends on your training program, experience, exercise technique, of an estimated 1RM is to provide a maximum-strength estimate based on a submaximal set, so you do not necessarily need to perform a maximum-eff fatigue, and other factors.
When Should You Recalculate Your 1RM?
Your estimated 1RM can change as your strength changes.
You may want to recalculate it when you achieve a new repetition record with a particular weight.
For example, if you previously performed 80 kg for 5 repetitions and later perform 85 kg for 5 repetitions, your estimated 1RM will increase.
Regularly updating your estimate can help keep percentage-based training calculations relevant.
1RM Calculator FAQs
1. What does 1RM stand for?
1RM stands for one-repetition maximum. It refers to the maximum weight you can lift for one complete repetition of a specific exercise.
2. How does a 1RM calculator work?
A 1RM calculator uses the weight you lifted and the number of repetitions you completed to estimate your maximum single-repetition strength using a mathematical formula.
3. Do I have to test my actual maximum?
No. One purpose of an estimated 1RM is to provide a maximum-strength estimate based on a submaximal set, so you do not necessarily need to perform a maximum-effort repetition.
4. Which 1RM formula does this calculator use?
The calculator provides four individual formulas: Epley, Brzycki, Lander, and Lombardi. It also provides an Average of All option.
5. What is the Epley formula?
The Epley formula used by the calculator is 1RM = Weight × (1 + Reps ÷ 30).
6. What is the Brzycki formula?
The Brzycki formula used by the calculator is 1RM = Weight × 36 ÷ (37 − Reps).
7. What is the Average of All option?
It calculates the Epley, Brzycki, Lander, and Lombardi estimates and then averages the four results to produce one estimated 1RM.
8. Can I calculate my 1RM in kilograms?
Yes. Select kilograms as the weight unit and enter your lifting weight in kilograms. The resulting 1RM and percentages will be displayed in kilograms.
9. Can I calculate my 1RM in pounds?
Yes. Select pounds and enter the weight in pounds. The calculator will display the estimated 1RM in pounds.
10. How many repetitions can I enter?
The calculator accepts between 1 and 20 repetitions.
11. What happens if I enter one repetition?
If you enter one repetition, the calculator uses the weight you entered as your 1RM rather than estimating it with one of the formulas.
12. Why are my results different when I change formulas?
Each formula uses a different mathematical equation. Consequently, the same weight and repetition count can produce different estimated 1RM values.
13. What does 80% of 1RM mean?
It means 80% of your estimated one-repetition maximum. For example, if your estimated 1RM is 100 kg, 80% is 80 kg.
14. Is an estimated 1RM guaranteed to be accurate?
No. An estimated 1RM is a mathematical approximation. Your actual maximum can differ depending on exercise, technique, fatigue, experience, and other factors.
15. Can I use this calculator for different exercises?
Yes. You can calculate an estimated 1RM for exercises such as the bench press, squat, deadlift, overhead press, and other strength exercises. Enter the weight and repetitions from the specific exercise you want to evaluate.
Final Thoughts
The 1RM Calculator makes it easy to estimate your one-repetition maximum without having to perform a true maximum-effort lift. Simply enter the weight you lifted, select pounds or kilograms, enter your repetitions, and choose one of the available estimation formulas.
The calculator supports the Epley, Brzycki, Lander, and Lombardi formulas, along with an option to average all four estimates. This gives you several ways to evaluate the same performance and see how different formulas affect your estimated maximum.
After calculating your 1RM, the tool automatically provides 90%, 85%, 80%, 75%, and 70% of that value. These numbers can serve as useful reference points when planning percentage-based strength workouts.
Remember that an estimated 1RM is an approximation rather than a guarantee of your actual maximum strength. Use the result as a practical training reference, consider your experience and current condition, and adjust training loads appropriately for the exercise and workout you are performing.