Enter the weight you lifted and your reps to estimate your 1RM with five formulas. Every result shows in lb and kg.
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DetailsExercise & Unit
Weight & Reps
Weight lifted
Reps completed
Warning above 10 reps
Estimated 1RM (average of 5 formulas)
Formula Comparison
The five formulas range from 208.1 lb to 217.3 lb (94.4 kg to 98.6 kg).
% of 1RM Chart
100%
213 lb
96.6 kg
95%
202.4 lb
91.8 kg
90%
191.7 lb
87 kg
85%
181.1 lb
82.1 kg
80%
170.4 lb
77.3 kg
75%
159.8 lb
72.5 kg
70%
149.1 lb
67.6 kg
65%
138.5 lb
62.8 kg
60%
127.8 lb
58 kg
50%
106.5 lb
48.3 kg
Rep Max Chart (1–12 Reps)
1 rep
213 lb
96.6 kg
2 reps
199.7 lb
90.6 kg
3 reps
193.6 lb
87.8 kg
4 reps
188 lb
85.3 kg
5 reps
182.6 lb
82.8 kg
6 reps
177.5 lb
80.5 kg
7 reps
172.7 lb
78.3 kg
8 reps
168.2 lb
76.3 kg
9 reps
163.9 lb
74.3 kg
10 reps
159.8 lb
72.5 kg
11 reps
155.9 lb
70.7 kg
12 reps
152.2 lb
69 kg
Based on the Epley formula rearranged: weight = 1RM ÷ (1 + reps ÷ 30). The 1-rep row is the estimated 1RM itself.
How a One Rep Max Calculator Estimates Your 1RM
Your one rep max (1RM) is the heaviest weight you can lift for a single rep on a given exercise. Instead of testing it directly, this calculator works backward from a set you already did. Enter the weight and the number of reps you completed, and it estimates the 1RM.
It runs five well-known formulas, Epley, Brzycki, Lombardi, O'Conner and Wathan, shows each result side by side, and uses their average as the headline number. Every result appears in both lb and kg.
From that estimate, the tool also builds a % of 1RM chart and a rep max chart for 1 to 12 reps, so you can see what a percentage or rep target works out to in actual weight.
Ways to Use Your Estimated Max
Bench, squat and deadlift max lookups
Enter a recent set of 3 to 8 reps and see where your max likely sits for each lift.
Working out percentages
Get the weight for 70%, 80% or 90% of your max in lb and kg from the percentage chart.
Comparing formulas
See how far apart Epley, Brzycki and the other three land for the same set.
Estimating other rep maxes
Check what a 3-rep, 5-rep or 10-rep weight your estimated 1RM implies using the rep max chart.
Comparing sets from different days
Convert sets of different weights and reps into one estimated 1RM so they are easier to compare.
How to Estimate Your Max in 4 Steps
- Pick an exercise and a unit (lb or kg). The exercise only labels your result.
- Enter the weight you lifted and the reps you completed (1 to 20).
- Read the estimated 1RM, then compare the five formulas in the bar list.
- Use the % of 1RM chart and the rep max chart for target weights, or copy the results.
Note: Results update as you type, and both lb and kg are always shown.
Limits of Rep-Based Estimates
- These are formula estimates. Your tested max can come in higher or lower.
- Above 10 reps the five formulas disagree more. For example, 100 lb for 20 reps ranges from about 135 lb to 212 lb across the formulas.
- The exercise you select only changes the label. Every lift uses the same formulas.
- Weight can be entered from 1 to 1,100 lb (500 kg) and reps from 1 to 20.
- The calculation runs in your browser, and the page does not send your numbers to a server.
1RM Formulas: Epley, Brzycki, Lombardi, O'Conner, Wathan
The equations this calculator uses, with a worked example. At 1 rep, every formula returns the weight you entered.
| Formula | Equation (w = weight, r = reps) | Example: 225 lb × 5 reps |
|---|---|---|
| Epley | w × (1 + r ÷ 30) | 262.5 lb |
| Brzycki | w × 36 ÷ (37 − r) | 253.1 lb |
| Lombardi | w × r^0.1 | 264.3 lb |
| O'Conner | w × (1 + 0.025 × r) | 253.1 lb |
| Wathan | 100 × w ÷ (48.8 + 53.8 × e^(−0.075 × r)) | 262.3 lb |
| Average (headline result) | Mean of the five results | 259.1 lb (117.5 kg) |
Example values are rounded to one decimal. The calculator uses the unrounded numbers.
Epley vs. Brzycki: Where the Formulas Agree and Differ
What changes between the formulas as the rep count goes up.
Estimating a max vs. testing it
A tested 1RM means working up to the heaviest single you can lift. A formula skips that step. It takes a set you already did, such as 185 lb for 5 reps, and projects it to one rep. The result is a projection, so your tested max can come in higher or lower.
Epley and Brzycki at different rep counts
Epley multiplies your weight by 1 + reps ÷ 30. Brzycki multiplies it by 36 ÷ (37 − reps). Both multipliers are about 1.33 at 10 reps. Below 10 reps, Epley gives the higher number. Above 10 reps, Brzycki pulls ahead. At 20 reps the multipliers are about 1.67 for Epley and 2.12 for Brzycki.
Why five formulas give five answers
Each formula uses a different curve to connect reps to a percentage of your max, so the answers split apart as reps increase. For 225 lb × 5 reps the five results span 253.1 to 264.3 lb. For 100 lb × 20 reps they span about 135 to 212 lb. That is why the calculator shows all five and averages them.
How the percentage and rep max charts are built
The % of 1RM chart multiplies the averaged 1RM by each percentage from 100% down to 50%. The rep max chart rearranges the Epley formula: weight = 1RM ÷ (1 + reps ÷ 30). The 1-rep row is the estimated 1RM itself.
Common Mistakes With Rep-Based Max Estimates
Entering a long set (15+ reps)
A 15 to 20 rep set gives the five formulas the most room to disagree, so the averaged result is a rough figure.
💡 See the solution▼
Mixing up lb and kg
Typing 185 while kg is selected treats it as 185 kg, which is about 408 lb.
💡 See the solution▼
Counting reps that do not match the lift
Partial-range or bounced reps raise your rep count and push the estimate up.
💡 See the solution▼
Relying on a single formula
Reading only the Epley number can hide a gap of several pounds between formulas.
💡 See the solution▼
Questions About Estimating a Max
Q.What is a one rep max (1RM)?
A. Your one rep max is the heaviest weight you can lift for a single rep on a given exercise. This calculator estimates it from a set you already did, such as 185 lb for 5 reps, so you do not have to test a single.
Q.Which formulas does this 1RM calculator use?
A. It uses five: Epley, Brzycki, Lombardi, O'Conner and Wathan. The large number at the top is the plain average of the five, and each formula's result is listed below it. If you enter 1 rep, the weight you entered is used as the 1RM and no formula is applied.
Q.Epley vs. Brzycki: which one is better?
A. Neither is marked as better here, so the tool shows both. They give the same result at 10 reps. Below 10 reps, Epley gives the higher number. Above 10 reps, Brzycki gives the higher one, and the gap grows quickly. At 20 reps, Epley multiplies your weight by about 1.67 and Brzycki by about 2.12.
Q.How many reps should I enter?
A. The calculator accepts 1 to 20 reps. It shows a warning above 10 reps because the five formulas spread further apart as reps go up. For example, 100 lb for 5 reps gives results from about 112.5 to 117.5 lb, while 100 lb for 20 reps gives results from about 135 to 212 lb.
Q.How is the rep max chart calculated?
A. It rearranges the Epley formula using the averaged 1RM: weight = 1RM ÷ (1 + reps ÷ 30). The 1-rep row is the estimated 1RM itself. The % of 1RM chart multiplies the averaged 1RM by each percentage from 100% down to 50%.
Q.Can I get results in both pounds and kilograms?
A. Yes. Pick lb or kg for your input and every result shows in both units, using 1 lb = 0.45359237 kg. Switching the unit converts the weight you already entered.
Q.Does the exercise I pick change the math?
A. No. The exercise (bench press, squat, deadlift, overhead press or other) only labels your result and the copied summary. All lifts use the same five formulas.
Q.Is the weight and rep data I enter sent anywhere?
A. No. The calculation runs in your browser, and this page does not send the weights or reps you type to a server.
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