---
title: "One Rep Max Calculator (Epley & Brzycki) | Boost Fitness"
canonical_url: "https://boostfitness.io/tools/one-rep-max-calculator"
last_updated: "2026-09-02T05:56:51.417Z"
meta:
  description: "Free one rep max calculator using the Epley and Brzycki formulas. Estimate your 1RM from any set of 1–12 reps and get a 50–95% loading table for programming."
  "og:description": "Free one rep max calculator using the Epley and Brzycki formulas. Estimate your 1RM from any set of 1–12 reps and get a 50–95% loading table for programming."
  "og:title": "One Rep Max Calculator (Epley & Brzycki) | Boost Fitness"
---

Boost Fitness

# One rep max calculator

**Estimate your 1RM from any hard set of 1–12 reps using the Epley and Brzycki formulas, then use the percentage table to set working weights for your programme. Free, instant, and no sign-up required.**

**Unit**

**Weight lifted (kg)**

**Reps completed (1–12)**

Epley

**116.5 kg**

Brzycki

**112.5 kg**

Average estimated 1RM

**114.5 kg**

**Percentage of 1RM loading table (based on the average estimate) **

| **% of 1RM ** | **Weight (kg) ** | **Approx. reps ** |
| --- | --- | --- |
| **95% ** | 109 | \~2 |
| **90% ** | 103 | \~3 |
| **85% ** | 97.5 | \~5 |
| **80% ** | 91.5 | \~8 |
| **75% ** | 86 | \~10 |
| **70% ** | 80 | \~13 |
| **65% ** | 74.5 | \~16 |
| **60% ** | 69 | \~20 |
| **55% ** | 63 | \~25 |
| **50% ** | 57.5 | \~30 |

## How this one rep max calculator works

A one rep max is the heaviest weight you can lift once with good technique. Rather than testing it directly, this calculator estimates it from a submaximal set using two of the most widely validated prediction equations:

- **Epley (1985):** 1RM = weight × (1 + reps ÷ 30)
- **Brzycki (1993):** 1RM = weight × 36 ÷ (37 − reps)

The two formulas agree closely in the 2–10 rep range and diverge slightly beyond it, so we show both alongside their average. If you lifted 100 kg for 5 reps, Epley estimates 116.5 kg and Brzycki 112.5 kg — an average of roughly 114.5 kg. For the most reliable estimate, use a recent set taken close to failure with solid form, ideally in the 2–6 rep range.

## Using the percentage table in your programming

Almost every structured strength programme prescribes loads as a percentage of 1RM, which is what the table above is for. As a rule of thumb: **85–95%** suits low-rep maximal strength work (1–5 reps), **65–80%** is the classic hypertrophy and strength-endurance zone (6–12 reps), and **50–60%** works well for technique practice, speed work, and warm-up progressions. The "approx. reps" column shows roughly how many reps most lifters manage at each load — useful as a sanity check when you're choosing working weights for a new block.

Coaches using [Boost Fitness](https://boostfitness.io/features/nutrition) typically estimate a client's 1RM from their logged working sets, then write programmes in percentages so the loads scale automatically as the client gets stronger.

## Limitations — and when a coach should adjust

Prediction formulas are population averages, and individuals vary. A few honest caveats:

- **High-rep sets overestimate less reliably.** Above 10–12 reps the rep-to-load relationship flattens, so estimates from a 15-rep set aren't trustworthy.
- **Estimates are exercise-specific.** Lifters usually get more reps at a given percentage on lower-body lifts (squat, leg press) than upper-body lifts (bench press, overhead press). Muscle fibre make-up and training history shift the curve too.
- **An estimate is not a green light for a max attempt.** Technique, mobility, and fatigue on the day all matter. Treat the number as a programming reference, not a promise.

A good coach adjusts when the data says so: if a client fails prescribed reps at 80%, the estimate is too high — recalculate from a recent set or drop the training max by 5–10%. Many coaches deliberately programme from 90% of estimated 1RM for exactly this reason. And remember that strength expression depends on recovery: sleep, stress, and nutrition (see our [protein intake calculator](https://boostfitness.io/tools/protein-intake-calculator) and [macro calculator](https://boostfitness.io/tools/macro-calculator) ) move the needle more than most lifters expect.

**Useful detail **

## Frequently asked questions

Your one rep max is the heaviest weight you can lift for a single repetition of an exercise with sound technique. Coaches use it as a reference point: most strength programmes prescribe working loads as a percentage of 1RM, so knowing it (or a good estimate) lets you load sessions consistently as you get stronger.

They agree almost exactly around 6–10 reps and diverge slightly outside that range: Brzycki tends to estimate a little lower at higher rep counts, Epley a little higher. Neither is universally "correct" — accuracy depends on the lifter and the exercise — which is why this calculator shows both plus the average. For programming purposes the average is a sensible starting point.

For most people, no. Maximal single attempts carry more injury risk and cause more fatigue than submaximal sets, and an estimate from a hard set of 3–6 reps is accurate enough to programme from. True 1RM testing is mainly useful for competitive powerlifters and weightlifters who need to practise maximal attempts for their sport.

The formulas are most reliable between about 2 and 6 reps, and reasonable up to around 10. Beyond 10–12 reps the relationship between reps and load flattens out and estimates drift, particularly for lower-body lifts — which is why this calculator caps input at 12 reps.

Whenever training performance changes meaningfully — typically every 4–8 weeks in a structured block. If your working sets start feeling easier at the prescribed percentages, or you hit a rep PR, re-estimate from a recent hard set and update the percentages you train from.

**Keep calculating **

## More free tools

[<h3>**Macro Calculator**</h3>Calories and macros for any goal — BMR (Mifflin-St Jeor), TDEE, and a protein/fat/carb split.](https://boostfitness.io/tools/macro-calculator) [<h3>**BMI Calculator**</h3>Body mass index in metric or imperial units, with NHS categories and honest limitations.](https://boostfitness.io/tools/bmi-calculator) [<h3>**Protein Intake Calculator**</h3>An evidence-based daily protein range (1.2–2.2 g/kg) for your body weight and goal.](https://boostfitness.io/tools/protein-intake-calculator)

From Boost Fitness — see [**nutrition coaching features **](https://boostfitness.io/features/nutrition), [**pricing **](https://boostfitness.io/pricing), or [**how we compare **](https://boostfitness.io/compare).

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