---
title: "Rule of 72 Calculator"
method: GET
path: "/api/calc/rule-of-72-calculator"
tags: ["Finance"]
---

# Rule of 72 Calculator

`GET /api/calc/rule-of-72-calculator`

## Request

- Base URL: `https://calcbright.com`
- URL: `https://calcbright.com/api/calc/rule-of-72-calculator`
- Auth: none declared

At 8% a year, money doubles in 72 ÷ 8 = 9 years. Enter any rate to compare the Rule of 72, the Rule of 69.3 and the exact compound-growth answer.

## Query parameters

- `rate` number: Annual rate of return (%)

## Response `200`

Calculation result

- CalcOutput
  - `ok` boolean
  - `tool` string
  - `name` string
  - `url` string: Open this link to see the full calculation
  - `inputs` object
  - `summary` string: Plain-text answer
  - `details` string
  - `result` object
  - `errors` object

## Other responses

- `400`: Invalid input (see errors)

---

[API](https://skmtc.dev/calcbright/apis/calcbright-calculator-api.md) · [All operations](https://skmtc.dev/calcbright/apis/calcbright-calculator-api/llms.txt) · [OpenAPI document](https://skmtc.dev/calcbright/apis/calcbright-calculator-api/revisions/f58229e56e58?raw)