Estimate your one-rep max from a completed set using pounds (lbs) or
kilograms (kg) for bench press, squat, deadlift, overhead press, and
other strength exercises.
Now that you know your estimated 1RM, use our
Barbell Plate Calculator
to see which plates to load for your next set.
The Science Behind One-Rep Max Prediction
Your one-rep max (1RM) is the heaviest weight you can successfully
complete for one repetition of a specific exercise using a defined
technique and range of motion. Testing a true 1RM can be demanding,
so many lifters use a submaximal set to estimate it instead.
This calculator uses four established repetition-based prediction
equations: Epley, Brzycki, Lander, and Lombardi. These equations
produce estimates rather than direct measurements, and different
formulas can give different results for the same set.
How to Use This 1RM Calculator
Enter the weight you lifted and the number of completed repetitions.
Choose pounds (lb) or kilograms (kg), select a formula, and calculate
your estimated one-rep max.
For a useful starting estimate, use a clean set performed with
consistent technique. Research on repetition-based prediction shows
that accuracy can vary with the number of repetitions, exercise,
population, and prediction equation, so the result should not be
treated as a guaranteed maximum.
A 1RM percentage chart helps translate your estimated maximum into
training loads. Strength programs commonly use percentages of 1RM to
describe training intensity, but the number of repetitions a person
can perform at a given percentage varies between exercises and
individuals.
90%–100%:
Very heavy loading commonly associated with low-repetition
strength work and maximal-strength practice.
80%–85%:
Moderate-to-heavy loading commonly used for strength-focused and
mixed strength/hypertrophy training.
70%–75%:
Moderate loading often used for higher-volume strength and
hypertrophy work.
60%–65%:
Lighter loading that can be useful for higher-repetition work,
technique practice, warm-ups, or other program-specific purposes.
These are general reference ranges, not fixed rules. Actual training
loads should reflect the exercise, program, training experience,
technique, fatigue, and recovery.
The NSCA describes percentage-of-1RM loading as one method for
prescribing resistance, while also noting that repetition capacity
at a given percentage can vary between exercises and individuals.
The 4 Core 1RM Formulas Explained
Each equation models the relationship between a submaximal weight and
the number of repetitions completed. Because the mathematical models
differ, the estimated 1RM can change depending on which formula you
select.
1. Epley Formula
1RM = Weight × (1 + Reps / 30)
The Epley equation is a commonly used repetition-based prediction
model and is frequently included in comparisons of 1RM equations.
2. Brzycki Formula
1RM = Weight × 36 / (37 − Reps)
The Brzycki equation is another widely used prediction model. Its
denominator reaches zero at 37 repetitions, so this calculator blocks
the formula at 37 reps and above.
3. Lander Formula
1RM = (100 × Weight) / (101.3 − 2.67123 × Reps)
The Lander equation uses a denominator that decreases as repetitions
increase. This calculator blocks inputs once that denominator is no
longer positive, preventing invalid or non-physical results.
4. Lombardi Formula
1RM = Weight × Reps^0.10
Lombardi uses a non-linear power relationship between repetitions and
estimated maximum strength. Research has evaluated Lombardi alongside
other repetition-based equations in specific populations, but no
single equation should be assumed to be universally most accurate.
Why Can 1RM Estimates Differ Between Exercises?
A prediction equation does not know your exercise technique, range of
motion, training history, fatigue profile, or individual strength
curve. The same person can therefore receive different-quality
estimates for different lifts.
Research on bench press has found useful prediction from
submaximal repetition performance, while also showing that prediction
behavior can change as repetitions increase. One study of 220 men
found stronger prediction performance when sets were at or below
10 repetitions and recommended caution when using higher-repetition
sets to estimate 1RM.
Research also shows that prediction accuracy can differ between
exercises and testing methods. Therefore, use your estimated 1RM as
a planning reference rather than assuming it is the exact weight you
can lift on a particular day.
Should the Barbell Weight Be Included?
Yes. If you are calculating a barbell lift, enter the total load you
actually lifted, including the bar and all plates.
A 45 lb (20 kg) Olympic-style bar is common in many gyms, but barbell
weights vary by bar type, manufacturer, and training environment.
Check the actual bar weight rather than assuming every bar has the
same unloaded weight.
When Should You Use an Estimated 1RM?
An estimated 1RM is useful when you want a practical strength reference
without performing a true maximal single. It can help with
percentage-based programming, tracking changes in strength, and
choosing starting loads.
A direct 1RM test is a different measurement: it tests the maximum
load you can successfully complete under the test conditions. It
requires appropriate preparation, technique, equipment, and judgment,
particularly when heavy free-weight lifts are involved.
If you prefer to work from a conservative training max, use our
Training Max Calculator
after estimating your 1RM.
Sources & References
The equations and concepts discussed on this page come from established
resistance-training and 1RM-prediction research. The cited studies
evaluate prediction equations in specific populations and exercises,
so their results should not be interpreted as proof that one formula
is universally best for every lifter.
RepMaths does not claim that any one formula is universally the most
accurate. Comparing multiple estimates can provide useful context,
especially when the input set is outside the range where a particular
equation has been studied.
Frequently Asked Questions
What is a 1RM calculator?
A 1RM calculator estimates the maximum weight you could lift for one
repetition from a lighter weight and completed repetition count. It
uses a mathematical prediction equation rather than directly testing
your maximum.
Which 1RM formula is the most accurate?
No formula is guaranteed to be the most accurate for every lifter,
exercise, or rep range. Epley, Brzycki, Lander, and Lombardi can
produce different estimates, so it is useful to treat the result as
an estimate rather than a guaranteed maximum.
Can I calculate my 1RM using more than 10 reps?
Yes, but prediction uncertainty can increase as the number of
repetitions rises, and different equations may diverge more.
Research on bench press has found useful prediction from
submaximal sets while supporting caution with higher-repetition
inputs.
Why can my 1RM estimate differ between bench press and squat?
1RM prediction accuracy can vary by exercise because different lifts
involve different movement patterns, muscle groups, technique
demands, and fatigue characteristics. A formula that gives a useful
estimate for one lift is not automatically equally accurate for
another.
Should I include the barbell weight in my 1RM calculation?
Yes. Enter the total load you lifted, including the bar and plates.
Because barbell weights vary, use the actual weight of the bar you
trained with rather than assuming a universal bar weight.
What is a 1RM percentage chart used for?
A 1RM percentage chart converts an estimated maximum into training
loads. Coaches and lifters commonly use percentages of 1RM to
describe training intensity, but the exact repetitions possible at
a percentage vary by person, exercise, and program.
Does this formula work the same for men and women?
These general prediction equations can be used with both men and
women. However, prediction accuracy can vary with the exercise,
population, training experience, repetition range, and testing
conditions.
Is estimating a 1RM better than testing a true 1-rep max?
An estimate can be a practical alternative when you do not want to
perform a true maximal single. A direct 1RM test measures actual
performance under the test conditions, but it involves heavier
loading and should be approached with appropriate technique,
preparation, equipment, and safety considerations.