ForHosting KIT · Math

Wastage allowance calculator

Find the quantity to order so that, after a known share is wasted, you still keep what you need: 100 units at 10% wastage means ordering 111.1111. The expected waste is shown too. Free in your browser.

Free
Runs in your browser
No sign-up
Your data stays on your device

Run — free How it works & API

Use it from WebAPIEmailTelegramApp soon

Worked example

If you enter

Desired net quantity: 100
Wastage %: 10
Decimal places: 4

You get

Gross quantity: 111.1111
Waste quantity: 11.1111

Gross quantity given wastage % and desired net. Search intent: wastage allowance calculator. No network calls or random seeds are required. Failed jobs are not billed.

What a wastage allowance is

Some of what you buy never reaches the finished job. A wastage allowance is the extra you order so that, after that share is lost, the net amount you actually need is still there. You give two things: the net quantity and the wastage percentage. The calculator returns the gross quantity to order and the waste quantity you can expect to lose. With 100 units needed and 10% wastage, the gross is 111.1111 and the waste is 11.1111. Your inputs are checked before any arithmetic and repeated next to the result, so you can confirm what was calculated.

Why you divide instead of adding

The wastage percentage is a share of what you order, not of what you need. That is why the gross is the net divided by one minus the rate. The most common slip is to add the percentage on top of the net: the order looks reasonable, but the waste, taken from the larger gross, eats into the amount you meant to keep, and you end up short. Another slip is rounding an intermediate figure and then reusing it. Here the result is rounded only once, at the end, to the decimals you choose, with halves rounded up.

What you can do with it

Teaching

Pinned goldens.

FAQ

What is the formula for a wastage allowance?

Gross equals net divided by one minus the wastage rate, with the rate written as a fraction of one hundred. The tool does this division for you and shows both the gross and the waste.

Why not simply add the wastage percentage to the net quantity?

Because the waste is lost from what you order, not from what you need. Adding the percentage on top leaves you a little short; dividing by one minus the rate gives the exact amount.

What does the waste quantity mean?

It is the part you expect to lose: the gross minus the net. For 100 units at 10% wastage it is 11.1111, which is 10% of the gross order.

How are the results rounded?

If you choose a number of decimals, the gross and the waste are rounded once at the end, with halves rounded up. Nothing is rounded along the way, so small errors do not pile up.

Related tools

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/math/wastage-allowance

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/math/wastage-allowance \
  -H "Authorization: Bearer $KIT_KEY" \
  -H "Content-Type: application/json" \
  -d '{"net_quantity":100,"wastage_percent":10}'

const res = await fetch("https://api.kit.forhosting.com/math/wastage-allowance", {
  method: "POST",
  headers: {
    "Authorization": `Bearer ${process.env.KIT_KEY}`,
    "Content-Type": "application/json"
  },
  body: JSON.stringify({
    "net_quantity": 100,
    "wastage_percent": 10
  })
});
const { task_id } = await res.json();

import os, requests

res = requests.post(
    "https://api.kit.forhosting.com/math/wastage-allowance",
    headers={"Authorization": f"Bearer {os.environ['KIT_KEY']}"},
    json={
    "net_quantity": 100,
    "wastage_percent": 10
},
)
task_id = res.json()["task_id"]

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

body := bytes.NewBufferString(`{"net_quantity":100,"wastage_percent":10}`)
req, _ := http.NewRequest("POST", "https://api.kit.forhosting.com/math/wastage-allowance", body)
req.Header.Set("Authorization", "Bearer "+os.Getenv("KIT_KEY"))
req.Header.Set("Content-Type", "application/json")
res, _ := http.DefaultClient.Do(req)

Example request

{
  "net_quantity": 100,
  "wastage_percent": 10
}

Example response

{
  "task_id": "tsk_a1b2c3d4e5f6a1b2c3d4e5f6",
  "type": "math.wastage_allowance",
  "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.

Technical notes

The calculator is free in the browser, deterministic, and identical on the API path. Inputs are validated before arithmetic so invalid payloads fail with invalid_input. Half-up rounding is applied once from raw IEEE values when decimals are requested. Use the same JSON from spreadsheets, CMS, automation, or teaching demos.

How it works

Gross quantity given wastage % and desired net. gross=net/(1−w/100). No network calls or random seeds are required. Failed jobs are not billed. No network calls or random seeds are required. Failed jobs are not billed. The calculator is free in the browser, deterministic, and identical on the API path. Inputs are validated before arithmetic so invalid payloads fail with invalid_input. Half-up rounding is applied once from raw IEEE values when decimals are requested. Use the same JSON from spreadsheets, CMS, automation, or teaching demos. The calculator is free in the browser, deterministic, and identical on the API path. Inputs are validated before arithmetic so invalid payloads fail with invalid_input. Half-up rounding is applied once from raw IEEE values when decimals are requested. Use the same JSON from spreadsheets, CMS, automation, or teaching demos.

Inputs, limits and rounding

Optional decimals use half-up once. Outputs echo inputs. No network calls or random seeds are required. Failed jobs are not billed. No network calls or random seeds are required. Failed jobs are not billed. Provide required JSON fields. Invalid types raise invalid_input. The calculator is free in the browser, deterministic, and identical on the API path. Inputs are validated before arithmetic so invalid payloads fail with invalid_input. Half-up rounding is applied once from raw IEEE values when decimals are requested. Use the same JSON from spreadsheets, CMS, automation, or teaching demos. The calculator is free in the browser, deterministic, and identical on the API path. Inputs are validated before arithmetic so invalid payloads fail with invalid_input. Half-up rounding is applied once from raw IEEE values when decimals are requested. Use the same JSON from spreadsheets, CMS, automation, or teaching demos.

When to use it

Use when search intent matches. Gross quantity given wastage % and desired net. No network calls or random seeds are required. Failed jobs are not billed. No network calls or random seeds are required. Failed jobs are not billed. The calculator is free in the browser, deterministic, and identical on the API path. Inputs are validated before arithmetic so invalid payloads fail with invalid_input. Half-up rounding is applied once from raw IEEE values when decimals are requested. Use the same JSON from spreadsheets, CMS, automation, or teaching demos. The calculator is free in the browser, deterministic, and identical on the API path. Inputs are validated before arithmetic so invalid payloads fail with invalid_input. Half-up rounding is applied once from raw IEEE values when decimals are requested. Use the same JSON from spreadsheets, CMS, automation, or teaching demos.

Integration use cases

Quick check

Free widget.

Automation

Same JSON via API.

Technical questions

Free?

Yes tier A.

Network?

No.

Bad input?

invalid_input.

API?

Yes.

Locales?

EN-only; Nitro hydrates.

Read the full KIT documentation →

Run — free