Cunningham Equation

Estimate daily caloric needs with the Cunningham equation, which bases resting metabolic rate (RMR) on lean body mass rather than total weight alone. It is often preferred for athletes and individuals with known body-fat percentage.

Formula (RMR)

RMR = 500 + 22 × lean body mass (kg)

Lean body mass = weight × (1 − body fat % ÷ 100). Enter weight, height, age, sex, and body-fat percentage; the tool derives lean mass and applies an activity multiplier for total daily expenditure.

Background

Published by Cunningham (1980), this approach reflects that metabolically active tissue—not fat—drives most energy expenditure at rest. It can track better than weight-only formulas when body composition is available.

When to use it

Suitable when you have a reliable body-fat estimate (DEXA, calipers, BIA) and want caloric targets that account for muscle mass, common in sports nutrition and recomposition planning.

Limitations

Accuracy depends heavily on body-fat measurement quality—consumer scales and handheld BIA devices can error by several percentage points. The original sample was athletic; very high adiposity or clinical conditions may reduce fit. Not validated for children or pregnancy.

Example

With weight 60 kg and height 180 cm, cunningham returns a numeric estimate.

This skill is available over A2A JSON-RPC and REST. When you already know the skill id and export, call execute directly—no discovery step required.

REST example

curl -sS -X POST https://toolplaza.app/api/helpers/execute \
  -H 'Content-Type: application/json' \
  -d '{"skillId":"caloric-needs__cunningham","export":"calculateCunninghamCalories","args":[{"weight":70,"fatMassPercent":25}]}'

A2A JSON-RPC example

Send POST https://toolplaza.app/api/a2a with:

{
  "jsonrpc": "2.0",
  "id": "1",
  "method": "message/send",
  "params": {
    "message": {
      "messageId": "uuid",
      "role": "user",
      "parts": [
        {
          "kind": "text",
          "text": "ignored"
        }
      ]
    },
    "metadata": {
      "toolplaza": {
        "skillId": "caloric-needs__cunningham",
        "export": "calculateCunninghamCalories",
        "args": [
          {
            "weight": 70,
            "fatMassPercent": 25
          }
        ]
      }
    }
  }
}

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