One Rep Max Calculator | Estimate Your 1RM from Weight and Reps (Epley, Brzycki, O'Conner and 4 More Formulas, Their Average, the NSCA Chart, RIR/RPE), Weights for 5, 8 or 10 Reps from Your 1RM (Rep Max Chart, %1RM), Barbell Plate Loading and Warm-up Sets, Weights and Reps by Goal, Glossary
The One Rep Max Calculator brings together the weight calculations of strength training, such as “if I can lift 80 kg 8 times, what is my max?”, “with a 1RM of 100 kg, what weight should I use for 10 reps?” and “which plates do I need for 100 kg?”. In the 1RM tab, enter the weight and reps you lifted to estimate your 1RM with seven formulas, Epley (W × (1 + R ÷ 30)), Brzycki (W × 36 ÷ (37 − R)), O'Conner (W × (1 + R ÷ 40), common in Japan), Lombardi, Lander, Mayhew and Wathan, and with the NSCA chart (100 kg × 10 reps gives 133.3 kg with Epley and 130.9 kg as the average of the seven formulas). You can also enter how many reps you had left (RIR/RPE), and your body weight to get a strength-to-body-weight ratio. The reps tab gives the weight you can lift for 1 to 20 reps (rep max chart) and weights and rough reps for each %1RM, rounded to your gym's plate increments such as 2.5 kg. The plates tab finds the plates to put on each side of the bar for a target weight, with the fewest plates for your bar (20 kg, 15 kg, etc.), collars and the plates your gym has, and lists warm-up weights with their plates. It also includes a %1RM-to-reps chart for each formula, weights and reps for strength, hypertrophy and muscular endurance, and a glossary of RIR, RPE and other terms. Switch between kg and lb (pounds) at any time.
Calculating your 1RM (max weight)
Estimate the most weight you can lift once (1RM) from how many times you lifted a weight in the bench press, squat, deadlift and other lifts.
Reps left in the tank (RIR)
Formula
Smooths out each formula's quirks. Use this if unsure
Rounding (your gym's plate increment)
Estimated 1RM
99.7 kg
Rounded: 100 kg
Weight lifted as % of 1RM
80.2%
Weight for 5 reps (5RM)
87.5 kg
For 10 reps: 75 kg
| Formula | Estimated 1RM | Formula |
|---|---|---|
| Average of 7 formulas | 99.7 kg | |
| Epley | 101.3 kg | W × (1 + R ÷ 30) |
| Brzycki | 99.3 kg | W × 36 ÷ (37 − R) |
| O'Conner | 96 kg | W × (1 + R ÷ 40) |
| Lombardi | 98.5 kg | W × R^0.10 |
| Lander | 100.1 kg | 100W ÷ (101.3 − 2.67123R) |
| Mayhew | 101 kg | 100W ÷ (52.2 + 41.9e^(−0.055R)) |
| Wathan | 102.1 kg | 100W ÷ (48.8 + 53.8e^(−0.075R)) |
| NSCA chart | 100 kg |
W is the weight lifted and R the reps. The formulas assume reps to failure and are rough guides: most accurate for 1–10 reps, and off by a few kg depending on the lift and your muscle type (fast- or slow-twitch).
When you test a real 1RM, warm up well and use a spotter or safety bars. Estimates are rough guides, so try a new weight a little lighter first.
ABOUT
About One Rep Max Calculator | Estimate Your 1RM from Weight and Reps (Epley, Brzycki, O'Conner and 4 More Formulas, Their Average, the NSCA Chart, RIR/RPE), Weights for 5, 8 or 10 Reps from Your 1RM (Rep Max Chart, %1RM), Barbell Plate Loading and Warm-up Sets, Weights and Reps by Goal, Glossary
The One Rep Max Calculator estimates the most weight you can lift once (1RM, your max) from the weight and reps you lifted in the bench press, squat, deadlift and other lifts. It also gives the weight for each number of reps from your 1RM (rep max chart) and shows which plates to load on a barbell for a target weight.
How to use One Rep Max Calculator | Estimate Your 1RM from Weight and Reps (Epley, Brzycki, O'Conner and 4 More Formulas, Their Average, the NSCA Chart, RIR/RPE), Weights for 5, 8 or 10 Reps from Your 1RM (Rep Max Chart, %1RM), Barbell Plate Loading and Warm-up Sets, Weights and Reps by Goal, Glossary
- 1In “Calculate 1RM”, enter the weight you lifted and the reps you did to failure (switch between kg and lb at the top)
- 2If you stopped short of failure, choose how many more reps you could have done (RIR)
- 3Choose a formula (if unsure, “average of 7 formulas”). The value from each formula is listed for comparison
- 4In “Weight by reps”, check the weight for 5, 8, 10 or other reps from your 1RM, and the weight for each %1RM
- 5In “Plate loading”, enter a target weight, choose your bar and the plates your gym has, and check the plates for each side
Great for
- Getting a rough idea of your bench press max without testing a true one-rep max
- Setting the weight for a program such as “8 reps at 80% of 1RM”
- Choosing a weight that suits your goal, such as hypertrophy (6–12 reps) or strength (1–5 reps)
- Converting past sets into a 1RM to compare progress
- Converting weights in lb (pounds) from overseas videos and apps into kg
- Knowing which plates to load for odd weights such as 102.5 kg
Good to know
- With W as the weight lifted and R as the reps, Epley is W × (1 + R ÷ 30), Brzycki is W × 36 ÷ (37 − R) and O'Conner is W × (1 + R ÷ 40). The “average of 7 formulas” divides by the average %1RM of the seven formulas, so converting the 1RM back to a weight by reps returns the original weight.
- All formulas assume the reps were done to failure and are rough guides. They are most accurate between 1 and 10 reps; above 12 reps the formulas differ a lot. If you choose an RIR, reps + RIR is used as the reps to failure.
- The NSCA chart is a %1RM table, such as 100% for 1 rep, 87% for 5, 80% for 8, 75% for 10, 67% for 12 and 65% for 15. Reps not in the table (13 and 14) are filled in on a straight line between the values either side.
- Plate loading combines the plates you select into the fewest plates for (target − bar) ÷ 2 − collar on each side. If the exact weight cannot be made, it gives the closest weight that does not go over the target.
- When you test a real 1RM, always warm up well and use a spotter or safety bars.
Questions this tool answers
Use One Rep Max Calculator | Estimate Your 1RM from Weight and Reps (Epley, Brzycki, O'Conner and 4 More Formulas, Their Average, the NSCA Chart, RIR/RPE), Weights for 5, 8 or 10 Reps from Your 1RM (Rep Max Chart, %1RM), Barbell Plate Loading and Warm-up Sets, Weights and Reps by Goal, Glossary for searches like these:
- Calculate my 1RM (max weight)
- Find my bench press max from reps
- Find the weight for 10 reps from my 1RM
- See a rep max chart
- Work out which plates to load on a barbell
- Convert weights between lb and kg
FAQ
- If I can lift 100 kg 10 times, what is my 1RM?
- 133.3 kg with the Epley formula, the Brzycki formula and the NSCA chart. The O'Conner formula (reps ÷ 40) gives a lower 125 kg, and the average of the seven formulas is 130.9 kg. Somewhere between about 125 and 135 kg is a realistic estimate.
- What is my bench press max if I can do 80 kg for 8 reps?
- About 99.7 kg as the average of the seven formulas, 101.3 kg with Epley, and exactly 100 kg with the NSCA chart (8 reps = 80%). “80 kg for 8 reps” is a handy rule of thumb for a 100 kg bench press.
- With a 1RM of 100 kg, what weight should I use for 10 reps?
- 75 kg with Epley, Brzycki and the NSCA chart, and about 76.4 kg as the average of the seven formulas. For 5 reps it is about 85–89 kg, and for 8 reps about 80 kg. Start a little lighter and go up on the next set if it feels easy.
- How many reps can I do at 80% of my 1RM?
- About 8 by the NSCA chart and 7–8 working back from the Epley formula. As a rough guide, 90% is 3–4 reps, 85% is 5–6, 75% is about 10, and 70% is 11–13.
- Which plates do I need for 100 kg?
- With a 20 kg bar you need 40 kg on each side, so two 20 kg plates per side. With competition collars (2.5 kg each side), it is 20 kg + 15 kg + 2.5 kg per side. For 102.5 kg, it is two 20 kg plates + 1.25 kg per side.
- How many kg is 225 lb?
- About 102.1 kg (1 lb = 0.45359237 kg). 225 lb, or “two plates”, is a 45 lb bar with two 45 lb plates on each side, and 315 lb (about 142.9 kg) is three per side.
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