One Rep Max Calculator
Estimate your one repetition maximum using three proven formulas.
What Is a One Rep Max?
Your one repetition maximum (1RM) is the heaviest weight you can lift for a single repetition of a given exercise. It is the gold standard for measuring muscular strength and is used to design training programmes that prescribe loads as a percentage of your 1RM.
The Three Formulas
- Epley: 1RM = weight × (1 + reps ÷ 30)
- Brzycki: 1RM = weight × (36 ÷ (37 − reps))
- Lombardi: 1RM = weight × reps0.10
Each formula estimates 1RM from a sub-maximal lift. Epley works well for moderate reps (up to ~10), Brzycki is more accurate for low reps (1–5), and Lombardi uses a power relationship suited to higher rep ranges.
Using the Percentage Table
Training programmes often prescribe loads as a percentage of your 1RM. The table below shows common percentages and their typical use:
- 95%: Near-maximal singles, testing.
- 90%: Heavy doubles and triples for peak strength.
- 85%: Sets of 3–5 reps for strength.
- 80%: Sets of 4–6 reps, a staple strength load.
- 75%: Sets of 6–8 reps bridging strength and hypertrophy.
Safety Tips
Testing a true 1RM carries injury risk and requires a spotter. Estimating from sub-maximal lifts is safer and nearly as useful for programming. Always warm up thoroughly, use proper form, and progress gradually. If you are new to strength training, work with a qualified coach to learn technique before testing maxes.
Frequently Asked Questions
A one rep max (1RM) is the maximum amount of weight you can lift for a single repetition of a given exercise. It is a common measure of muscular strength and is used to set training loads as a percentage of that maximum.
The Epley formula is widely used and works well for moderate rep ranges (up to about 10 reps). The Brzycki formula is more accurate for low reps (1-5). Lombardi uses a power relationship and suits higher rep ranges. This calculator shows all three so you can compare.
The percentage table shows the weight you should lift for a given percentage of your 1RM. For example, 80% of your 1RM is a common load for building strength with sets of 3-5 reps. Lower percentages (50-70%) are used for speed and power work.