One Rep Max Calculator

HealthInstant resultsFormula shown100% in your browser

Estimate your 1RM from any set and get the working weights for 60–95% of it.

Inputs

Weight lifted (kg)

Reps completed

How to use this calculator: One Rep Max Calculator

Estimate your 1RM from any set and get the working weights for 60–95% of it. The example below is calculated by this page's real engine from the displayed inputs.

1Confirm that the One Rep Max Calculator matches the quantity or design check you need.
2Enter Weight lifted and Reps completed using the units printed beside each field.
3Check every value before calculating, especially decimal points and measurement units.
4Calculate, then follow the substituted equations in the worked example and compare the result with any stated limit.
5Read the assumptions, warnings and cited references before using the result for a financial, medical or engineering decision.

Input guide and example values

Use values from the same measurement basis and time period. Conditional fields appear only when the related option is selected.

Input	Example value	Why it matters
Weight lifted	80 kg	Measured or known weight lifted used by the calculation engine.
Reps completed	8	Measured or known reps completed used by the calculation engine.

Formula inputs & variables for One Rep Max Calculator

These are the named quantities used by this calculator. When the source formula does not define a mathematical symbol, OneCalcApp keeps the real input label instead of inventing one.

Variable / input	Unit	Meaning in this calculation
Weight lifted	kg	Measured or known weight lifted used by the calculation engine.
Reps completed	—	Measured or known reps completed used by the calculation engine.

How the One Rep Max Calculator works

The One Rep Max Calculator uses Weight lifted and Reps completed to calculate Estimated 1RM, 95% — 2 reps, 85% — 5 reps, 75% — 8–10 reps, and 60% — warm-up. Its engine applies Epley: 1RM = w × (1 + reps/30); the worked values below come from that same live calculation rather than a separately typed example.

With Weight lifted 80 kg and Reps completed 8, the main worked-example result is Estimated 1RM = 100.3 kg.

How each One Rep Max Calculator input is used

Weight lifted

The One Rep Max Calculator worked example uses Weight lifted = 80 kg. This value is passed directly into the calculation, with an allowed minimum 0.

Reps completed

The One Rep Max Calculator worked example uses Reps completed = 8. This value is passed directly into the calculation, with an allowed minimum 1 and maximum 15.

One Rep Max Calculator formulas and result interpretation

Formula 1: relationship used

In the One Rep Max Calculator, Epley: 1RM = w × (1 + reps/30). The quantities in this relationship come from the named inputs or from an earlier calculation step shown in the worked example.

Formula 2: relationship used

In the One Rep Max Calculator, Brzycki: 1RM = w × 36 / (37 − reps). The quantities in this relationship come from the named inputs or from an earlier calculation step shown in the worked example.

Estimated 1RM

For the displayed One Rep Max Calculator worked example, Estimated 1RM is 100.3 kg. Verify Weight lifted and Reps completed and their units before relying on this output.

95% — 2 reps

For the displayed One Rep Max Calculator worked example, 95% — 2 reps is 95.3 kg. Verify Weight lifted and Reps completed and their units before relying on this output.

85% — 5 reps

For the displayed One Rep Max Calculator worked example, 85% — 5 reps is 85.3 kg. Verify Weight lifted and Reps completed and their units before relying on this output.

75% — 8–10 reps

For the displayed One Rep Max Calculator worked example, 75% — 8–10 reps is 75.2 kg. Verify Weight lifted and Reps completed and their units before relying on this output.

60% — warm-up

For the displayed One Rep Max Calculator worked example, 60% — warm-up is 60.2 kg. Verify Weight lifted and Reps completed and their units before relying on this output.

One Rep Max Calculator accuracy, checks and limitations

One Rep Max Calculator units check: confirm Weight lifted (kg) and Reps completed before calculating.
One Rep Max Calculator result check: compare Estimated 1RM, 95% — 2 reps, 85% — 5 reps, 75% — 8–10 reps, and 60% — warm-up with the substituted formula steps and the displayed rounding precision.
One Rep Max Calculator: This is a general estimate, not a diagnosis or personal medical advice. Discuss health decisions with a qualified clinician.

Formula, derivation and worked example

Estimating a one-rep max from a set you already did is safer than testing a true max. Accuracy is best under 10 reps; beyond that fatigue distorts the estimate.

Epley: 1RM = w × (1 + reps/30)

Brzycki: 1RM = w × 36 / (37 − reps)

Substitution steps

1. Epley
w(1 + r/30)
= 101.3 kg
2. Brzycki
w·36/(37−r)
= 99.3 kg

Computed example results

Estimated 1RM: 100.3 kg
95% — 2 reps: 95.3 kg
85% — 5 reps: 85.3 kg
75% — 8–10 reps: 75.2 kg
60% — warm-up: 60.2 kg

Understanding the result

Read the main result together with supporting checks, assumptions, limits and intermediate values.

For a manual check, repeat the first equation, confirm the units and change one input at a time.

Assumptions and calculation scope

Weight lifted is assumed to be entered in kg; converting from another unit before entry avoids changing the numerical meaning of the calculation.
One Rep Max Calculator applies the displayed Epley: 1RM = w × (1 + reps/30) relationship to the entered health inputs. Factors that are not exposed as inputs or stated assumptions are outside this calculator's calculation scope.

Common mistakes when using One Rep Max Calculator

Do not mix units for Weight lifted (kg). A unit mismatch changes the input magnitude even when the typed number looks reasonable.
Do not replace the displayed Epley: 1RM = w × (1 + reps/30) relationship with a different convention without also changing the underlying assumptions; compare like-for-like methods when checking the result.
Do not treat Estimated 1RM = 100.3 kg from the worked example as a universal answer. It belongs to the displayed example inputs and must be recalculated for the actual case.

When the One Rep Max Calculator is useful

One Rep Max Calculator is designed for cases where Weight lifted, Reps completed are known and you need Estimated 1RM, 95% — 2 reps, 85% — 5 reps. The page keeps the live calculator, calculation method and worked example together so the result can be checked instead of treated as a black-box number.

Use the calculator for the scope described by its inputs and notes. The displayed method is Epley: 1RM = w × (1 + reps/30). If the real project or decision needs factors that are not represented here, treat the result as an estimate and add the missing checks separately.

Weight lifted and Reps completed: what changes the answer

The worked example uses Weight lifted = 80 kg, Reps completed = 8. With those values, Estimated 1RM is 100.3 kg. Changing an input should be interpreted according to that field's unit, range, option and hint rather than by the number alone.

For this calculator, the main input roles are: Weight lifted (kg): Measured or known weight lifted used by the calculation engine. Reps completed: Measured or known reps completed used by the calculation engine.

How to sanity-check a One Rep Max Calculator result

Start by confirming the entered values and units, then compare the substituted working with the displayed formula or calculation steps. Pay particular attention to Estimated 1RM, because it is the first worked-example output shown by the live engine.

Finally, compare the result with the assumptions, warnings and related calculators on this page. A nearby calculator can be useful as a cross-check when it measures the same workflow from a different input or output direction.

Next logical calculator

Continue with Lean Body Mass Calculator

Lean Body Mass Calculator is directly connected from One Rep Max Calculator as a source-defined continuation or comparison.

Open Lean Body Mass Calculator

Formula

Epley: 1RM = w × (1 + reps/30)
Brzycki: 1RM = w × 36 / (37 − reps)

Estimating a one-rep max from a set you already did is safer than testing a true max. Accuracy is best under 10 reps; beyond that fatigue distorts the estimate.

Frequently asked questions

What inputs does the One Rep Max Calculator use?

It uses Weight lifted and Reps completed. Follow the unit printed for each field and choose any selectable option to match the real scenario.

What does the One Rep Max Calculator calculate?

It calculates Estimated 1RM, 95% — 2 reps, 85% — 5 reps, 75% — 8–10 reps, and 60% — warm-up. With the displayed default inputs, Estimated 1RM is 100.3 kg.

Which formula does the One Rep Max Calculator use?

The primary relationship is Epley: 1RM = w × (1 + reps/30). The page also shows substituted values and calculation steps so the result can be checked independently.

How can I verify a One Rep Max Calculator result?

First verify the units for Weight lifted and Reps completed. Then compare the substituted formula steps with Estimated 1RM and its displayed precision.

What are the limitations of the One Rep Max Calculator?

One Rep Max Calculator: This is a general estimate, not a diagnosis or personal medical advice. Discuss health decisions with a qualified clinician.

Where can I find related Health tools?

Use the related-tools section on this page to compare another method, change units or continue the same health calculation.

Related calculators

Keep going with more health tools.

Lean Body Mass Calculator

Calculate lean body mass from weight and height using the Boer formula.

Protein Intake Calculator

Find your daily protein target in grams based on weight, activity and your goal.

Macro Calculator

Split your daily calories into protein, carbohydrate and fat grams for your chosen goal.

Pace Calculator

Convert distance and finish time into pace per km, per mile and average speed.

Blood Pressure Calculator

Classify a blood pressure reading and see pulse pressure and mean arterial pressure.

Running Calorie Calculator

Calculate calories burnt running at any pace and duration.