One-Rep Max (1RM) Calculator

Estimates your one-rep max (1RM) from a weight and the reps you completed, using seven formulas, with a 50–100% chart and the plates to load on each side of the bar.

How to use

1. On the "1RM" tab, choose the "Unit" and enter the "Weight lifted" and "Reps completed".
2. Read the "Estimated 1RM", the results "By formula" and the "Percentage chart".
3. Pick a lift and press "Save to records" to keep your best per lift on the "Records" tab.
4. On the "Plates" tab, enter the "Total weight wanted" and choose the "Bar" to see the "Plates on each side".

How it works

• The estimate is the plain mean of seven formulas: Epley, Brzycki, Lombardi, O'Conner et al., Lander, Mayhew et al. and Wathan. With one rep, the weight lifted is the 1RM.
• Estimates are most useful for 1–12 reps; with more reps the formulas spread apart. Up to 30 reps can be entered.
• The plate calculator uses "Your plates", which you can edit, and as few plates as possible.
• This is an estimate. If you attempt a true one-rep max, do it with a spotter. Records and plates are saved on this device.

Questions and answers

How do I calculate my one-rep max?

The Epley formula is weight × (1 + reps ÷ 30). For 100 kg lifted 5 times that is about 116.7 kg; the Brzycki formula, weight × 36 ÷ (37 − reps), gives 112.5 kg.

Why do the 1RM formulas give different results?

Each was built on different groups of people and lifts, so the page shows the range and the average of all seven.

How many reps can I do at 80% of my 1RM?

Reversing the Epley and Brzycki formulas gives about 8 reps. The real number varies between people and lifts.

What plates do I need for 100 kg?

With a 20 kg bar you need 40 kg per side; with the default plate set that is one 25 kg and one 15 kg plate.