ForHosting KIT · Developer Utilities

Hair growth calculator

This hair growth calculator estimates how long hair will be after a given number of months, starting from a measured initial length and a constant average monthly growth rate.

● BetaFree · in your browser

Run — free How it works & API

Use it from WebAPIEmailTelegramApp soon

The model is linear: projected length equals initial length plus months times the monthly rate, so the same units you type for length and rate come back on the projected figure — centimetres with centimetres per month, inches with inches per month. Typical human scalp hair grows near one and a quarter centimetres, or about half an inch, each month, but you can enter any average you have measured on your own head or in a salon log. Negative months and a negative growth rate are rejected as invalid input because elapsed time cannot run backwards and this estimator does not model shrinkage or breakage as a negative rate. The same deterministic arithmetic runs free in the browser and through the API at $0.002 per successful call, with no network, no sampling, and no clock.

How to use it

Enter your values in the form above. The tool checks them before calculating and shows the result on the same page.

Check your inputs

Use the labels and units shown next to each field. If something is missing or outside the allowed range, the page points to the field to fix.

Use it again or automate it

Use the browser tool for individual checks and the API when you need the same capability in an automated workflow.

What you can do with it

Get an answer now

Enter one set of values and see the result without building a spreadsheet or script.

Compare scenarios

Change one value at a time and rerun the calculation to understand what affects the result.

Automate repeated work

Use the API when the same calculation needs to run inside your product or workflow.

FAQ

How do I use this capability?

Complete the fields above and run it on this page. The form highlights anything that needs attention.

For developers — API access

Everything on this page is available programmatically. This section is for teams who want to wire it into their own systems; everyone else can just use the tool above.

API endpoint

POSThttps://api.kit.forhosting.com/life/hair-growth

Prefer to automate it? One authenticated POST creates the task; the result comes back by webhook or a signed link. The same capability also runs here on the web, by email and from Telegram — and soon from our app too.

Call it from your stack

curl -X POST https://api.kit.forhosting.com/life/hair-growth \
  -H "Authorization: Bearer $KIT_KEY" \
  -H "Content-Type: application/json" \
  -d '{"initial_length":10,"months":6,"growth_rate":1.25}'

const res = await fetch("https://api.kit.forhosting.com/life/hair-growth", {
  method: "POST",
  headers: {
    "Authorization": `Bearer ${process.env.KIT_KEY}`,
    "Content-Type": "application/json"
  },
  body: JSON.stringify({
    "initial_length": 10,
    "months": 6,
    "growth_rate": 1.25
  })
});
const { task_id } = await res.json();

import os, requests

res = requests.post(
    "https://api.kit.forhosting.com/life/hair-growth",
    headers={"Authorization": f"Bearer {os.environ['KIT_KEY']}"},
    json={
    "initial_length": 10,
    "months": 6,
    "growth_rate": 1.25
},
)
task_id = res.json()["task_id"]

<?php
$res = file_get_contents("https://api.kit.forhosting.com/life/hair-growth", false, stream_context_create([
  "http" => [
    "method"  => "POST",
    "header"  => "Authorization: Bearer " . getenv("KIT_KEY") . "\r\nContent-Type: application/json",
    "content" => '{"initial_length":10,"months":6,"growth_rate":1.25}',
  ],
]));
$task = json_decode($res, true);

body := bytes.NewBufferString(`{"initial_length":10,"months":6,"growth_rate":1.25}`)
req, _ := http.NewRequest("POST", "https://api.kit.forhosting.com/life/hair-growth", body)
req.Header.Set("Authorization", "Bearer "+os.Getenv("KIT_KEY"))
req.Header.Set("Content-Type", "application/json")
res, _ := http.DefaultClient.Do(req)

Example request

{
  "initial_length": 10,
  "months": 6,
  "growth_rate": 1.25
}

Example response

{
  "task_id": "tsk_a1b2c3d4e5f6a1b2c3d4e5f6",
  "type": "life.hair_growth",
  "status": "queued",
  "_links": {
    "result": "/tasks/tsk_…/result"
  }
}

The API is asynchronous: the call returns a task_id immediately and the result arrives by webhook. Polling is capped at 1 req/s per task.

Pricing

Per request$0.002

Published price — no tokens, no invented credits. A failed task is never charged.

Errors

HTTP	Code	Meaning
`401`	`unauthorized`	Missing or invalid API key.
`402`	`insufficient_balance`	Your balance doesn't cover the task price.
`404`	`unknown_type`	That task type doesn't exist.
`429`	`rate_limited`	Too many requests. Use the webhook instead of polling.

Read the full KIT documentation →