---
title: "Estimate one-rep max from a set and its RPE"
method: GET
path: "/api/tools/rpe-estimate-max"
---

# Estimate one-rep max from a set and its RPE

`GET /api/tools/rpe-estimate-max`

## Request

- Base URL: `https://www.ironledger.app`
- URL: `https://www.ironledger.app/api/tools/rpe-estimate-max`
- Auth: none declared

Estimate a one-rep max from weight, reps and RPE, treating RPE as reps in reserve (RPE 8 = 2 reps left) and applying the one-rep max formula to reps + reps in reserve.

Method: Reps in reserve = 10 − RPE (Zourdos et al. 2016). The set is treated as reps + reps in reserve to failure, then Epley or Brzycki is applied.

## Query parameters

- `weight` number, required: Weight lifted for the set.
- `reps` integer, required: Reps completed, 1 to 20.
- `rpe` number, required: Rating of perceived exertion, 5 to 10, read as reps in reserve (RPE 8 = 2 reps left). Half points allowed.
- `unit` 'kg' | 'lb': Weight unit for every load in and out: kg or lb.
- `formula` 'epley' | 'brzycki': One-rep max formula: epley (weight × (1 + reps ÷ 30), the one the IronLedger app uses) or brzycki (weight × 36 ÷ (37 − reps)).

## Response `200`

The result, a one-line summary, the method used and a link to the same result on the site.

- object
  - `tool` string, required
  - `version` string
  - `summary` string, required
  - `result` object, required
  - `method` string
  - `url` string, uri, required

## Other responses

- `400`: An input is missing or out of range.
- `429`: Too many requests from this address.

---

[API](https://skmtc.dev/ironledger/apis/ironledger-strength-calculators-api.md) · [All operations](https://skmtc.dev/ironledger/apis/ironledger-strength-calculators-api/llms.txt) · [OpenAPI document](https://skmtc.dev/ironledger/apis/ironledger-strength-calculators-api/revisions/265d7ad551b5?raw)