One Rep Max Calculator – A Simple Way To Measuring Your Strength

Training intensity refers to the difficulty of a certain movement or exercise. It’s determined by the weight used. This is one of the main training determinants alongside exercise volume (amount of work performed) and rest. 

Your one repetition maximum, or 1RM, refers to the amount of weight you can lift for one repetition with good form. It’s the peak force your muscles can generate for each exercise. 

Knowing your 1RM gives you a measure of your maximal strength for each exercise. This allows you to set your training intensity, track progress, and improve exercise safety. 

Our one rep max calculator provides you with a quick and easy estimation of your 1RM for each exercise. It uses your weight lifted and repetitions performed. The output gives you your 1RM and estimated rep ranges. 

We explain how to use one 1RM calculator below, detailing how it works and what it can be used for.

How To Use Our One Rep Max Calculator

Input Data

Perform a suitable warm-up for your chosen exercise. Start with some short-duration cardio followed by some dynamic stretches. After this, perform a couple of warm-up sets.

Choose a weight you can lift for multiple repetitions, ideally between one and ten. Perform as many repetitions as possible with proper form. Use the technique guides and tips to inform your training. Correct technique is important for targeting the correct muscle groups and reducing injury risk.

Record the weight lifted and amount of repetitions performed. Then, follow these steps when using our calculator:

1. Input the weight lifted in kilograms or pounds.
2. Input the number of repetitions performed (between one and ten). 
3. Set the results to either kilograms or pounds.
4. Choose one of three 1RM formulas. 
5. Click calculate.

Output Data

Once you click calculate, our one rep max calculator uses one of the three main formulations described below. The output allows you to change the formula used to compare the differences. 

At the top of the calculator output, you’ll have your 1RM number. This will be given to one decimal place. 

Underneath, you will have a table that shows your estimated rep maxes. This gives you the amount of weight you can lift for 1–20 repetitions.

Formulas Used To Calculate 1RM

Our one rep max calculator gives you three scientific formulas to choose from. These have been picked from many widely used formulas as the most common and accepted ones.  

• Epley Formula — 1RM = Weight Lifted x ( 1 + 30 ÷ Number Of Repetitions). 
• Brzycki Formula — 1RM = Weight Lifted x 36 ÷ 37 – Number Of Repetitions. 
• Lombardi Formula — 1RM = Weight Lifted × Number of Repetitions. 

Each formulation may have its advantages and disadvantages. The choice of calculation will depend on your preferences and research. 

For men, the Lombardi formula has been suggested to be the most accurate. In women, this difference seems to be non-significant. 

The accuracy of the calculation may also depend on the exercise. In the study linked above, none of the equations accurately predicted 1RM for the arm curl exercise. However, the accuracy of the squat and bench press was much higher.

The results of this study suggest that it may be easier to predict 1RM using compound, multi-joint exercises. The accuracy will also depend on the formula used and for what gender. 

You can also use each one and see which you think is closest to your true 1RM. This calculation can then be used going forward. 

Limitations Of The Calculator

The quick and easy measurements used come with certain limitations that need to be considered. These should be put into context when deciding if the calculator is right for you.

The main limitation of our one rep max calculator is accuracy. It gives you a useful estimation of your 1RM rather than a set tested value. Variables not considered that may influence the reading include:

• Gender (Male Vs Female).
• Exercise Form Used. 
• Muscle Fibre Composition (Percentages Of Type 1 And Type 2 Fibers).
• Exercise Used (Compound Vs Isolation).

This gives you a useful estimation with a varying degree of accuracy. In most cases, the 1RM reading should be close to the true value. In others, your 1RM may differ. 

How To Know Your 1RM Physically

Directly measuring your 1RM requires you to physically test what you can lift. This uses a process of trial and error where you increase the difficulty in small increments. 

While this will be more accurate than the one rep max calculator, it takes more time and requires equipment.

Follow these steps for a direct measurement:

1. Perform A Suitable Warm-Up — The prevalence of weight training injuries is 10%–82% depending on the sport. A warm-up should consist of aerobic exercise and some dynamic stretches. This loosens your joints, increases muscle temperature, and improves blood flow. 
2. Select A Suitable Weight — Choose a weight that’s around 50%–70% of your estimated 1RM. Perform one or two warm-up sets. 
3. Slowly Increase The Difficulty — Increase the weight in small 5%–10% increments. Perform one repetition each time, resting for 2–3 minutes between sets. Keep repeating the same process. 
4. Continue Until Your Maximal Effort — Stop when you can no longer perform one repetition using the proper form. The weight used before this is your true 1RM. 
5. Record Your 1RM Value — Ensure you write this number down. This can be used to check and monitor progress. 

Always consult with a qualified healthcare professional before starting a new exercise program or testing your 1RM. Ensure that safety is your main focus when performing the testing procedure. If in doubt, stop exercise immediately and consult a professional. 

Why Knowing Your 1RM Is Important?

Knowing your 1RM can be used for much more than just bragging to your friends. Here are some of the main applications once you’ve worked it out: 

• Personalized Training — Knowing your 1RM allows you to tailor your exercise intensity to your strength level. This is especially important during strength and power events for optimal progress. With this, you can set your training at the right level and make adjustments based on your ability and goals. 
• Progress Tracking — After setting your initial 1RM, you can test it again throughout your training to measure progress. This allows you to see if your training is working as intended. 
• Compare the results throughout your periodized program and adjust accordingly. This refers to a training program that intentionally changes the main training variables for the body to adapt. Examples include increasing exercise intensity and training volume. 
• Proper Weight Selection — Your 1RM allows you to choose the right intensity for each specific exercise and goal. What you lift on your bench press is very different from your bicep curl. Knowing this gives you the proper weight selection for your training routine. 
• Safety — Using the right weight for your ability level allows you to maintain the important technique cues for each exercise. This helps to keep a stable lifting position and prevent possible injury. With this, you can exercise with a higher safety level. 
• Goal Setting — Whether you’re training for strength, muscle size, or general fitness, you’ll likely have a goal in mind. Knowing your 1RM informs better goal setting when trying to lift a specific weight. You can set your number and time frame once you have it. 

Conclusion

Knowing your one repetition maximum gives you much more than just a number. It allows you to personalize your training, track progress, set goals, and increase safety. This gives you a versatile measure that should be used as you progress to an intermediate level. 

Our one rep max calculator is a quick and easy way to calculate your 1RM for each lift. It shows your 1RM value using popular scientific formulas. Alongside this, you have an estimated rep max chart to inform your programming.

Frequently Asked Questions