One Rep Max Calculator (1RM)

Strength estimate toolkit

Estimate one rep max, then inspect every load

Enter one completed set, choose a named equation, and compare the estimated 1RM across repetitions and percentages without mixing formulas.

1–10 repskg + lb4 formulas

Production-authorized calculationFormula 1.1.0. Estimates remain exercise- and population-dependent.

Formula-linked results

Estimated max weight by repetition

Every value below uses the unrounded Epley estimate and your selected output unit.

116.71

109.42

106.13

102.94

100.05

97.26

94.67

92.18

89.79

87.510

Weight (kg)Repetitions

Repetition view

Reps → weight

Estimated weight for 1–10 repetitions
Reps	Weight	% of 1RM
1	116.7 kg	100%
2	109.4 kg	94%
3	106.1 kg	91%
4	102.9 kg	88%
5	100.0 kg	86%
6	97.2 kg	83%
7	94.6 kg	81%
8	92.1 kg	79%
9	89.7 kg	77%
10	87.5 kg	75%

Percentage view

% of 1RM → weight

Percentage-based load reference
% of 1RM	Weight	Projected reps
100%	116.7 kg	1
95%	110.8 kg	1
90%	105.0 kg	3
85%	99.2 kg	5
80%	93.3 kg	7
75%	87.5 kg	10
70%	81.7 kg	>10*
65%	75.8 kg	>10*
60%	70.0 kg	>10*
55%	64.2 kg	>10*
50%	58.3 kg	>10*

* Values beyond 10 repetitions are outside this calculator's evidence boundary, so the exact extrapolated count is intentionally hidden. These tables are mathematical references, not workout prescriptions.

Formula scope and lifting safety

A one rep max (1RM) is the greatest load associated with one correctly completed repetition for a specific exercise and technique. “IRM” is not a separate metric here; it is a common mistyping of 1RM.

All four equations estimate rather than measure maximum strength. Accuracy varies by exercise, training status, technique, and the number of repetitions completed. Mayhew was developed for bench press, while the other equations also have exercise-specific limits.

Do not treat an estimate as permission to attempt a maximal lift. Use suitable supervision, equipment, technique, and medical clearance where appropriate.

Submaximal strength estimate

Estimate One-Rep Max Without Turning the Result into a Loading Command

A technically consistent set of one through ten repetitions can estimate a one-repetition maximum with Epley, Brzycki, Lombardi, or the bench-press-specific Mayhew equation. The calculator preserves pounds or kilograms and shows the selected model. It does not establish that attempting the predicted load is safe.

Side-by-side guide · Submaximal strength estimate

Select an Equation for Its Evidence Rather Than Its Highest Answer

Evidence boundary: 1–10 correct repetitions
Method choice: Four explicit prediction equations
One-rep input: Returned as the observed load

Epley, Brzycki, and Lombardi
These formulas apply different mathematical curves to load and repetition count. Their estimates diverge as repetitions rise, so choosing whichever produces the biggest number introduces result shopping.
Mayhew bench-press branch
The exponential Mayhew equation came from bench-press endurance data. Its presence does not make it an all-exercise model, and the calculator labels that specificity.
Direct single repetition
When one correct repetition is entered, the observed load is returned. No prediction multiplier is needed, but that still does not prove the lift was a true physiological maximum.

Estimate One-Rep Max Without Turning the Result into a Loading Command: A technically consistent set of one through ten repetitions can estimate a one-repetition maximum with Epley, Brzycki, Lombardi, or the bench-press-specific Mayhew equation. The calculator preserves pounds or kilograms and shows the selected model. It does not establish that attempting the predicted load is safe.

Use a Set Whose Technique Makes the Repetition Count Meaningful

The repetition input is not simply how many times a weight moved. The evidence assumes a consistent exercise, range of motion, tempo, and correctly completed set taken to technical failure. Stop counting when position or range changes. A five-repetition bench set with controlled pauses is not interchangeable with five shortened repetitions after form breaks down.

Record the exercise variation, equipment, load, unit, repetitions, and chosen equation. The same numeric answer can mean something different on a barbell, selectorized machine, or dumbbell movement. For a broader view of training context, the VO2 max field estimator evaluates aerobic field protocols; it does not validate lifting readiness or predict strength.

Select an Equation for Its Evidence Rather Than Its Highest Answer

Epley, Brzycki, and Lombardi

These formulas apply different mathematical curves to load and repetition count. Their estimates diverge as repetitions rise, so choosing whichever produces the biggest number introduces result shopping.

Mayhew bench-press branch

The exponential Mayhew equation came from bench-press endurance data. Its presence does not make it an all-exercise model, and the calculator labels that specificity.

Direct single repetition

When one correct repetition is entered, the observed load is returned. No prediction multiplier is needed, but that still does not prove the lift was a true physiological maximum.

Turn an Estimate into a Conservative Training Reference

Repeat the method, not just the number
Track progress with the same lift variation and equation. Changing both at once can create an apparent gain that comes entirely from methodology.
Use percentages as arithmetic
A displayed percentage table multiplies the estimate; it does not prescribe sets, repetitions, rest intervals, frequency, or progression.
Support recovery independently
The protein calculator can show an adult reference range, while the sleep planner can check bed-to-wake opportunity. Neither can convert this estimate into a personalized program.

Recognize Situations That Need Coaching or Clinical Clearance

Do not attempt a predicted maximum because a web result appears attainable. Heavy single repetitions can cause injury, especially without suitable experience, spotters, safeties, and exercise-specific preparation.
Pain, dizziness, chest discomfort, fainting, unusual breathlessness, recent injury, surgery, pregnancy, or a relevant medical condition calls for qualified guidance rather than a formula-derived load.
Novices, older adults, rehabilitation patients, and athletes using specialized technique may not match the source populations or exercise conditions.
Do not infer muscle mass or body composition from 1RM. The body-fat estimator is a separate measurement model with its own uncertainty.

Interpret Formula Disagreement as Uncertainty Information

Different equations can produce different 1RM estimates from the same set because they were derived or evaluated under different conditions. That disagreement is useful: it shows why the result should be treated as a range of plausible training reference values, not a hidden measurement. Prediction error also varies by exercise and repetition count, which is why this implementation rejects more than ten repetitions.

A sensible log keeps technique notes and submaximal performance alongside the calculated value. Improvement in a repeatable set may be meaningful even when the exact predicted maximum is uncertain. This calculator is not medical advice, rehabilitation guidance, or a substitute for a qualified strength professional who can observe the movement and select an appropriate progression.

Important limitations

One Rep Max Calculator (1RM) returns estimated one-repetition maximum, estimate-to-load multiplier, formula used, and load unit used only for the stated population, method, and source period. It is an informational calculation rather than a diagnosis, treatment plan, dosing instruction, exposure assessment, or individualized clinical recommendation.

Review the stated scope, calculation method, assumptions, supported inputs, and effective dates, and obtain qualified advice before using a high-stakes result.

This formula passed its registered engineering tests and is published under an explicit site-owner policy authorization. No independent expert, QA, editorial, legal, or third-party review is claimed. Verify consequential results with a qualified professional.

This subject may affect health, finance, tax, legal, or other consequential decisions. It has not received an independent domain-expert review; consult a qualified professional before relying on it.

Submaximal strength estimate

Estimate One-Rep Max Without Turning the Result into a Loading Command

Side-by-side guide · Submaximal strength estimate

Select an Equation for Its Evidence Rather Than Its Highest Answer

Evidence boundary: 1–10 correct repetitions
Method choice: Four explicit prediction equations
One-rep input: Returned as the observed load

Epley, Brzycki, and Lombardi
These formulas apply different mathematical curves to load and repetition count. Their estimates diverge as repetitions rise, so choosing whichever produces the biggest number introduces result shopping.
Mayhew bench-press branch
The exponential Mayhew equation came from bench-press endurance data. Its presence does not make it an all-exercise model, and the calculator labels that specificity.
Direct single repetition
When one correct repetition is entered, the observed load is returned. No prediction multiplier is needed, but that still does not prove the lift was a true physiological maximum.

Use a Set Whose Technique Makes the Repetition Count Meaningful

Select an Equation for Its Evidence Rather Than Its Highest Answer

Epley, Brzycki, and Lombardi

Mayhew bench-press branch

The exponential Mayhew equation came from bench-press endurance data. Its presence does not make it an all-exercise model, and the calculator labels that specificity.

Direct single repetition

When one correct repetition is entered, the observed load is returned. No prediction multiplier is needed, but that still does not prove the lift was a true physiological maximum.

Turn an Estimate into a Conservative Training Reference

Repeat the method, not just the number
Track progress with the same lift variation and equation. Changing both at once can create an apparent gain that comes entirely from methodology.
Use percentages as arithmetic
A displayed percentage table multiplies the estimate; it does not prescribe sets, repetitions, rest intervals, frequency, or progression.
Support recovery independently
The protein calculator can show an adult reference range, while the sleep planner can check bed-to-wake opportunity. Neither can convert this estimate into a personalized program.

Recognize Situations That Need Coaching or Clinical Clearance

Do not attempt a predicted maximum because a web result appears attainable. Heavy single repetitions can cause injury, especially without suitable experience, spotters, safeties, and exercise-specific preparation.
Pain, dizziness, chest discomfort, fainting, unusual breathlessness, recent injury, surgery, pregnancy, or a relevant medical condition calls for qualified guidance rather than a formula-derived load.
Novices, older adults, rehabilitation patients, and athletes using specialized technique may not match the source populations or exercise conditions.
Do not infer muscle mass or body composition from 1RM. The body-fat estimator is a separate measurement model with its own uncertainty.

One Rep Max Calculator (1RM)

Estimate one rep max, then inspect every load

Enter the lift you performed

Estimated max weight by repetition

Reps → weight

% of 1RM → weight

Estimate One-Rep Max Without Turning the Result into a Loading Command

Select an Equation for Its Evidence Rather Than Its Highest Answer

Epley, Brzycki, and Lombardi

Mayhew bench-press branch

Direct single repetition

Use a Set Whose Technique Makes the Repetition Count Meaningful

Select an Equation for Its Evidence Rather Than Its Highest Answer

Epley, Brzycki, and Lombardi

Mayhew bench-press branch

Direct single repetition

Turn an Estimate into a Conservative Training Reference

Recognize Situations That Need Coaching or Clinical Clearance

Interpret Formula Disagreement as Uncertainty Information

Important limitations

Estimate one rep max, then inspect every load

Enter the lift you performed

Estimated max weight by repetition

Reps → weight

% of 1RM → weight

Estimate One-Rep Max Without Turning the Result into a Loading Command

Select an Equation for Its Evidence Rather Than Its Highest Answer

Epley, Brzycki, and Lombardi

Mayhew bench-press branch

Direct single repetition

Use a Set Whose Technique Makes the Repetition Count Meaningful

Select an Equation for Its Evidence Rather Than Its Highest Answer

Epley, Brzycki, and Lombardi

Mayhew bench-press branch

Direct single repetition

Turn an Estimate into a Conservative Training Reference

Recognize Situations That Need Coaching or Clinical Clearance

Interpret Formula Disagreement as Uncertainty Information