One Rep Max Calculator
Use this one-rep max calculator to estimate your 1RM from the weight you lifted and number of reps completed.
Updated August 8, 2026
Calculated instantly in your browser — nothing is sent to or stored on our servers.
Medical Disclaimer: This calculator provides a general estimate based on established research and is for educational purposes only, not a substitute for medical advice. Individual results can vary based on health conditions, so consult a qualified healthcare professional or registered dietitian before making significant changes to your diet, exercise, or health routine. Read our full Medical Disclaimer.
How One Rep Max (1RM) Is Calculated
Your one-rep max (1RM) is the most weight you could lift for a single repetition. Testing it directly is risky, so most lifters estimate it from a lighter set taken to or near failure instead.
What This Calculator Measures
This gives a predicted 1RM from a single submaximal set, not a tested max. Treat it as a planning tool for setting training percentages, not a number to attempt directly without a proper warm-up.
The Formula
This calculator uses the Epley formula, one of the most commonly used 1RM estimates and one that has held up well against other formulas in independent comparison studies².
1RM = weight lifted × (1 + reps ÷ 30)
How This Calculator Computes Your Result
Enter the weight you lifted and the number of reps you completed on that set. We apply the Epley formula directly and round to one decimal place.
How Epley Compares to Other Formulas
Epley isn’t the only widely used prediction equation. A comparison of several 1RM formulas against actual tested maxes in the bench press, squat, and deadlift found that most common formulas, including Epley, Brzycki, and others, performed similarly well within the low-rep ranges they were built for, with prediction error increasing as rep count rises².
Formula | Equation |
Epley | 1RM = weight × (1 + reps ÷ 30) |
Brzycki | 1RM = weight × 36 ÷ (37 − reps) |
The two formulas are built on different assumptions about how quickly strength drops off as reps increase, and typically land within a few pounds of each other at moderate rep counts, but can diverge more as reps climb¹.
A Note on Accuracy
This formula is most accurate for sets of about 10 reps or fewer. Higher-rep sets tend to overestimate true one-rep max. Use your estimated 1RM to plan training percentages, not as a target to attempt directly without proper warm-up and spotting. Prediction accuracy decreases as rep count rises, and results can vary more for smaller-muscle or technically demanding exercises.
Frequently Asked Questions
How accurate are one-rep max estimates?
Formulas like Epley and Brzycki are generally accurate within a small margin for rep ranges of about 1 to 10², but accuracy decreases at higher rep counts.
Which formula does this calculator use?
The Epley formula, one of the most widely used and well-validated formulas for estimating one-rep max from submaximal lifts¹.
Should I ever test my true one-rep max?
Occasional supervised testing can be useful, but estimating from submaximal sets is generally safer and sufficient for programming most training.
Why does my estimated max seem off for some lifts?
Estimation formulas work best for compound lifts performed with consistent form. Technical or smaller-muscle exercises can produce less reliable estimates².
Sources
One Rep Max Calculator
Use this one-rep max calculator to estimate your 1RM from the weight you lifted and number of reps completed.
Updated August 8, 2026
Calculated instantly in your browser — nothing is sent to or stored on our servers.
Medical Disclaimer: This calculator provides a general estimate based on established research and is for educational purposes only, not a substitute for medical advice. Individual results can vary based on health conditions, so consult a qualified healthcare professional or registered dietitian before making significant changes to your diet, exercise, or health routine. Read our full Medical Disclaimer.
How One Rep Max (1RM) Is Calculated
Your one-rep max (1RM) is the most weight you could lift for a single repetition. Testing it directly is risky, so most lifters estimate it from a lighter set taken to or near failure instead.
What This Calculator Measures
This gives a predicted 1RM from a single submaximal set, not a tested max. Treat it as a planning tool for setting training percentages, not a number to attempt directly without a proper warm-up.
The Formula
This calculator uses the Epley formula, one of the most commonly used 1RM estimates and one that has held up well against other formulas in independent comparison studies².
1RM = weight lifted × (1 + reps ÷ 30)
How This Calculator Computes Your Result
Enter the weight you lifted and the number of reps you completed on that set. We apply the Epley formula directly and round to one decimal place.
How Epley Compares to Other Formulas
Epley isn’t the only widely used prediction equation. A comparison of several 1RM formulas against actual tested maxes in the bench press, squat, and deadlift found that most common formulas, including Epley, Brzycki, and others, performed similarly well within the low-rep ranges they were built for, with prediction error increasing as rep count rises².
Formula | Equation |
Epley | 1RM = weight × (1 + reps ÷ 30) |
Brzycki | 1RM = weight × 36 ÷ (37 − reps) |
The two formulas are built on different assumptions about how quickly strength drops off as reps increase, and typically land within a few pounds of each other at moderate rep counts, but can diverge more as reps climb¹.
A Note on Accuracy
This formula is most accurate for sets of about 10 reps or fewer. Higher-rep sets tend to overestimate true one-rep max. Use your estimated 1RM to plan training percentages, not as a target to attempt directly without proper warm-up and spotting. Prediction accuracy decreases as rep count rises, and results can vary more for smaller-muscle or technically demanding exercises.
Frequently Asked Questions
How accurate are one-rep max estimates?
Formulas like Epley and Brzycki are generally accurate within a small margin for rep ranges of about 1 to 10², but accuracy decreases at higher rep counts.
Which formula does this calculator use?
The Epley formula, one of the most widely used and well-validated formulas for estimating one-rep max from submaximal lifts¹.
Should I ever test my true one-rep max?
Occasional supervised testing can be useful, but estimating from submaximal sets is generally safer and sufficient for programming most training.
Why does my estimated max seem off for some lifts?
Estimation formulas work best for compound lifts performed with consistent form. Technical or smaller-muscle exercises can produce less reliable estimates².
Sources
One Rep Max Calculator
Use this one-rep max calculator to estimate your 1RM from the weight you lifted and number of reps completed.
Updated August 8, 2026
Calculated instantly in your browser — nothing is sent to or stored on our servers.
Medical Disclaimer: This calculator provides a general estimate based on established research and is for educational purposes only, not a substitute for medical advice. Individual results can vary based on health conditions, so consult a qualified healthcare professional or registered dietitian before making significant changes to your diet, exercise, or health routine. Read our full Medical Disclaimer.
How One Rep Max (1RM) Is Calculated
Your one-rep max (1RM) is the most weight you could lift for a single repetition. Testing it directly is risky, so most lifters estimate it from a lighter set taken to or near failure instead.
What This Calculator Measures
This gives a predicted 1RM from a single submaximal set, not a tested max. Treat it as a planning tool for setting training percentages, not a number to attempt directly without a proper warm-up.
The Formula
This calculator uses the Epley formula, one of the most commonly used 1RM estimates and one that has held up well against other formulas in independent comparison studies².
1RM = weight lifted × (1 + reps ÷ 30)
How This Calculator Computes Your Result
Enter the weight you lifted and the number of reps you completed on that set. We apply the Epley formula directly and round to one decimal place.
How Epley Compares to Other Formulas
Epley isn’t the only widely used prediction equation. A comparison of several 1RM formulas against actual tested maxes in the bench press, squat, and deadlift found that most common formulas, including Epley, Brzycki, and others, performed similarly well within the low-rep ranges they were built for, with prediction error increasing as rep count rises².
Formula | Equation |
Epley | 1RM = weight × (1 + reps ÷ 30) |
Brzycki | 1RM = weight × 36 ÷ (37 − reps) |
The two formulas are built on different assumptions about how quickly strength drops off as reps increase, and typically land within a few pounds of each other at moderate rep counts, but can diverge more as reps climb¹.
A Note on Accuracy
This formula is most accurate for sets of about 10 reps or fewer. Higher-rep sets tend to overestimate true one-rep max. Use your estimated 1RM to plan training percentages, not as a target to attempt directly without proper warm-up and spotting. Prediction accuracy decreases as rep count rises, and results can vary more for smaller-muscle or technically demanding exercises.
Frequently Asked Questions
How accurate are one-rep max estimates?
Formulas like Epley and Brzycki are generally accurate within a small margin for rep ranges of about 1 to 10², but accuracy decreases at higher rep counts.
Which formula does this calculator use?
The Epley formula, one of the most widely used and well-validated formulas for estimating one-rep max from submaximal lifts¹.
Should I ever test my true one-rep max?
Occasional supervised testing can be useful, but estimating from submaximal sets is generally safer and sufficient for programming most training.
Why does my estimated max seem off for some lifts?
Estimation formulas work best for compound lifts performed with consistent form. Technical or smaller-muscle exercises can produce less reliable estimates².