ForHosting KIT · Developer Utilities

Battery runtime calculator

This battery runtime calculator turns usable stored energy in watt-hours and a constant load power in watts into the operating time you can expect before the pack is empty.

● BetaFree · in your browser

Run — free How it works & API

Use it from WebAPIEmailTelegramApp soon

The relation is fully deterministic: time in hours equals energy in watt-hours divided by power in watts, which is the same first-order energy balance used on datasheets, UPS labels, and portable-power marketing when efficiency and Peukert effects are ignored. Zero energy with a positive load yields zero runtime; zero load is rejected because division by zero would imply infinite run time rather than a usable number. Small checks you may already know include one hundred watt-hours into a ten-watt load for ten hours, fifty watt-hours into a twenty-five-watt load for two hours, and seventy-two watt-hours into a twelve-watt load for six hours. The engine uses only finite arithmetic with no network calls, no sampling, and no date-dependent shortcuts. Use it free in the browser for homework, field sizing, and design checks, or call the API at $0.002 per successful request when you need reproducible runtime fixtures in CI, tutoring software, or teaching demos.

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/elec/battery-runtime-wh

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/elec/battery-runtime-wh \
  -H "Authorization: Bearer $KIT_KEY" \
  -H "Content-Type: application/json" \
  -d '{"energy_wh":100,"power_w":10}'

const res = await fetch("https://api.kit.forhosting.com/elec/battery-runtime-wh", {
  method: "POST",
  headers: {
    "Authorization": `Bearer ${process.env.KIT_KEY}`,
    "Content-Type": "application/json"
  },
  body: JSON.stringify({
    "energy_wh": 100,
    "power_w": 10
  })
});
const { task_id } = await res.json();

import os, requests

res = requests.post(
    "https://api.kit.forhosting.com/elec/battery-runtime-wh",
    headers={"Authorization": f"Bearer {os.environ['KIT_KEY']}"},
    json={
    "energy_wh": 100,
    "power_w": 10
},
)
task_id = res.json()["task_id"]

<?php
$res = file_get_contents("https://api.kit.forhosting.com/elec/battery-runtime-wh", false, stream_context_create([
  "http" => [
    "method"  => "POST",
    "header"  => "Authorization: Bearer " . getenv("KIT_KEY") . "\r\nContent-Type: application/json",
    "content" => '{"energy_wh":100,"power_w":10}',
  ],
]));
$task = json_decode($res, true);

body := bytes.NewBufferString(`{"energy_wh":100,"power_w":10}`)
req, _ := http.NewRequest("POST", "https://api.kit.forhosting.com/elec/battery-runtime-wh", body)
req.Header.Set("Authorization", "Bearer "+os.Getenv("KIT_KEY"))
req.Header.Set("Content-Type", "application/json")
res, _ := http.DefaultClient.Do(req)

Example request

{
  "energy_wh": 100,
  "power_w": 10
}

Example response

{
  "task_id": "tsk_a1b2c3d4e5f6a1b2c3d4e5f6",
  "type": "elec.battery_runtime_wh",
  "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.

Limits

max_abs_value 1000000000000000

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