ForHosting KIT · Developer Utilities

Ovulation calculator

Ovulation calculator: enter your values and see a clear result on this page. Free for individual checks; API from $0.002.

● BetaFree · in your browser

Run — free How it works & API

Use it from WebAPIEmailTelegramApp soon

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

What formula does it use?

Ovulation is placed at cycle_days minus luteal_days after the LMP. The fertile window is that offset minus 5 to plus 1 day, and next_period is the LMP plus cycle_days.

What are the default cycle and luteal lengths?

cycle_days defaults to 28 (valid 20-45) and luteal_days defaults to 14 (valid 10-16). Omit them to use the defaults.

What date format does lmp need?

A strict YYYY-MM-DD string, validated against the real UTC calendar. Impossible dates like 2026-02-30 return an invalid_input error.

Is it free, or does the API cost?

The on-page widget is free (tier A). The API is deterministic and priced from $0.002 per call, charged only on success.

Is this medical advice?

No. It is a general estimate based on average cycle timing and should not be used as contraception or a substitute for a clinician.

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/dev/ovulation-calculator

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/dev/ovulation-calculator \
  -H "Authorization: Bearer $KIT_KEY" \
  -H "Content-Type: application/json" \
  -d '{"lmp":"2026-03-01"}'

const res = await fetch("https://api.kit.forhosting.com/dev/ovulation-calculator", {
  method: "POST",
  headers: {
    "Authorization": `Bearer ${process.env.KIT_KEY}`,
    "Content-Type": "application/json"
  },
  body: JSON.stringify({
    "lmp": "2026-03-01"
  })
});
const { task_id } = await res.json();

import os, requests

res = requests.post(
    "https://api.kit.forhosting.com/dev/ovulation-calculator",
    headers={"Authorization": f"Bearer {os.environ['KIT_KEY']}"},
    json={
    "lmp": "2026-03-01"
},
)
task_id = res.json()["task_id"]

<?php
$res = file_get_contents("https://api.kit.forhosting.com/dev/ovulation-calculator", false, stream_context_create([
  "http" => [
    "method"  => "POST",
    "header"  => "Authorization: Bearer " . getenv("KIT_KEY") . "\r\nContent-Type: application/json",
    "content" => '{"lmp":"2026-03-01"}',
  ],
]));
$task = json_decode($res, true);

body := bytes.NewBufferString(`{"lmp":"2026-03-01"}`)
req, _ := http.NewRequest("POST", "https://api.kit.forhosting.com/dev/ovulation-calculator", body)
req.Header.Set("Authorization", "Bearer "+os.Getenv("KIT_KEY"))
req.Header.Set("Content-Type", "application/json")
res, _ := http.DefaultClient.Do(req)

Example request

{
  "lmp": "2026-03-01"
}

Example response

{
  "task_id": "tsk_a1b2c3d4e5f6a1b2c3d4e5f6",
  "type": "dev.ovulation_calculator",
  "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 →

Run — free