01
Your set
weight × repskg
reps
Best accuracy from a heavy set of 2–5 reps taken close to failure.
Enter any set — weight and reps — and get your estimated 1RM, training percentages, and the plates to load. Works in kg and lb.
Best accuracy from a heavy set of 2–5 reps taken close to failure.
| Intensity | Load (kg) | Typical reps |
|---|---|---|
| 95% | 109.5 | 2 |
| 90% | 103.5 | 4 |
| 85% | 98 | 6 |
| 80% | 92 | 8 |
| 75% | 86.5 | 10 |
| 70% | 80.5 | 12 |
| 65% | 75 | 15 |
| 60% | 69 | 18 |
| 55% | 63.5 | 20 |
| 50% | 57.5 | 25 |
Per side, on a 20 kg bar = 115 kg total.
Everything you need to use the number well — what a 1RM is, how the estimate is calculated, and how to train off it.
Your one-rep max is the heaviest weight you can lift for a single repetition with good form on a given exercise. Coaches use it as the reference point for programming: training loads are usually written as a percentage of 1RM, e.g. 5 sets of 5 at 80%.
Your set is run through the four standard formulas and the results are averaged, with the spread shown so you can see how confident the estimate is:
Example: 100 kg for 5 reps gives 116.7, 112.5, 117.5 and 112.5 — an estimated 1RM of about 115 kg. The formulas agree closely at low reps and drift apart above 8–10 reps.
Estimates from a set of 1–5 reps are typically within a few percent of a tested max. Accuracy drops as reps rise: at 10+ reps the formulas diverge and muscular endurance starts to matter more than strength. For the best estimate, use a heavy set of 2–5 reps taken close to failure.
For most lifters, estimating is safer and just as useful. A true max attempt carries injury risk, needs a spotter, and disrupts training for days. Estimating from a heavy set of 3–5 gives you a programming number without those costs. Competitive powerlifters test maxes in structured peaking blocks, not week to week.
No single formula wins on every lift and rep range. Epley and Brzycki are the most widely used; Lombardi and O'Conner bracket them. This calculator averages all four and shows the spread, which is a more honest answer than any one formula alone.
Roughly: 85–95% for 2–5 reps builds maximal strength, 70–80% for 6–10 reps builds strength and muscle, 55–65% for 12+ reps builds work capacity. Use the percentage table as a starting point, then adjust to how the weight actually moves — the estimate is a guide, not a contract.
It assumes a standard 20 kg (or 45 lb) Olympic bar and the plates found in most gyms — 20 / 15 / 10 / 5 / 2.5 / 1.25 kg, or 45 / 35 / 25 / 10 / 5 / 2.5 lb — and shows the plates for one side. If a weight can't be loaded exactly, it rounds down to the nearest loadable weight and says so. The target starts at your estimated 1RM rounded to a loadable weight; type any other number to plan a working set.
Log your sets in FitSync and your estimated 1RM for every lift updates automatically, with progress charts and an AI coach that programs off it. Free on iOS, Android and web.
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