One-rep max (Epley / Brzycki) API

Estimate one-rep max from a sub-maximal set via Epley (w·(1+reps/30)) and Brzycki (w·36/(37−reps)), with a rep-percentage training table. Answers 'what's my 1RM', 'one-rep max from 100kg x 5', 'estimate max bench', 'training weights for 80% of 1RM'.

Price$0.01per request

MethodPOST

Route/v1/health/one-rep-max

StatusLive

MIME typeapplication/json

Rate limit120/minute

CacheNo cache

healthone-rep-max1rmepleybrzyckistrengthliftingcalculator

API URLhttps://x402.hexl.dev/v1/health/one-rep-max

Integration docs

Example request

{
  "weight": 100,
  "reps": 5
}

Example response

{
  "oneRepMax": 116.7,
  "method": "Epley",
  "epley": 116.7,
  "brzycki": 112.5,
  "formula": "Epley: w*(1 + reps/30); Brzycki: w*36/(37-reps)",
  "inputs": {
    "weight": 100,
    "reps": 5
  },
  "repPercentages": [
    {
      "reps": 1,
      "percent": 100,
      "weight": 116.7
    },
    {
      "reps": 5,
      "percent": 87,
      "weight": 101.5
    },
    {
      "reps": 10,
      "percent": 75,
      "weight": 87.5
    }
  ]
}

Input schema

{
  "type": "object",
  "required": [
    "weight",
    "reps"
  ],
  "properties": {
    "weight": {
      "type": "number",
      "description": "Weight lifted (kg or lb)",
      "examples": [
        100
      ]
    },
    "reps": {
      "type": "number",
      "description": "Reps performed (1-36)",
      "examples": [
        5
      ]
    }
  }
}

Output schema

{
  "type": "object",
  "additionalProperties": true
}