Shopping budget tracker
With a budget of 100 and milk, bread, eggs and apples totalling 10.53, you have 89.47 left. The balance after every item shows which addition would tip the cart over before you reach the checkout. Free in your browser.
- Free
- Runs in your browser
- No sign-up
- Your data stays on your device
Run — free
Worked example
- Budget
- 100
- Item count
- 4
- Total spent
- 10.53
- Remaining
- 89.47
- Over amount
- 0
A shopping budget tracker answers one practical question before you reach the checkout: after this running list of item prices, how much money is still left, and have you already gone over? Shoppers, household planners, and small retail tools need a deterministic answer that does not scrape store catalogs or invent tax rates. This shopping budget tracker calculator accepts a total budget and one or more cart lines with prices, sums the spend, subtracts it from the budget, and returns remaining funds, whether the budget is exceeded, how far over you are when it is, and a running remaining balance after every line so you can see which addition tipped the cart. Failed validation—missing budget, empty lists, negative prices—is rejected as invalid input and is not billed.
How remaining funds and over-budget status are computed
Start with a non-negative shopping budget in any currency unit you already use for shelf prices—the calculator does not convert currencies or apply exchange rates. For each cart line, take a finite non-negative price; optional names label the line for display. Total spent is the sum of every price in the list.
Remaining funds equal the budget minus that total. When remaining is zero or positive, you are still within budget; when remaining is strictly negative, the budget is exceeded and the over amount is the absolute value of remaining. Zero budget is allowed: any positive spend is reported as over budget, which matches envelope-style rules where the allowance was already exhausted.
Free samples at price zero are accepted and do not change the total. Negative budgets and negative prices are rejected because they do not describe a physical shopping allowance or shelf price in this product.
What you can do with it
Weekly grocery envelope
Enter your weekly food budget and aisle prices as you shop; watch remaining funds and stop when the cart would go over.
Shared household cart
Roommates post a common budget and a joint item list so everyone sees the same total spent, remaining, and over-budget flag.
FAQ
How does the shopping budget tracker calculator work?
Send a non-negative budget and a non-empty list of item prices.
What happens if I go over budget?
Exceeding the budget is not treated as invalid input.
Can item prices be zero?
Yes. Free samples or promo lines at price 0 are allowed.
Do I need names on every cart line?
No. Names are optional. Bare numbers are treated as prices, and unnamed lines receive stable labels such as Item 1 for display.
How can I tell which item pushed the cart over budget?
Look at the balance shown after each line. The tracker subtracts every price in order, so the first line where the remaining amount drops below zero is the item that tipped the cart over.
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
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/shopping-budget \
-H "Authorization: Bearer $KIT_KEY" \
-H "Content-Type: application/json" \
-d '{"budget":100,"items":[{"name":"Milk 1 L","price":1.49},{"name":"Bread","price":2.25},{"name":"Eggs (12)","price":3.8},{"name":"Apples 1 kg","price":2.99}]}'const res = await fetch("https://api.kit.forhosting.com/life/shopping-budget", {
method: "POST",
headers: {
"Authorization": `Bearer ${process.env.KIT_KEY}`,
"Content-Type": "application/json"
},
body: JSON.stringify({
"budget": 100,
"items": [
{
"name": "Milk 1 L",
"price": 1.49
},
{
"name": "Bread",
"price": 2.25
},
{
"name": "Eggs (12)",
"price": 3.8
},
{
"name": "Apples 1 kg",
"price": 2.99
}
]
})
});
const { task_id } = await res.json();import os, requests
res = requests.post(
"https://api.kit.forhosting.com/life/shopping-budget",
headers={"Authorization": f"Bearer {os.environ['KIT_KEY']}"},
json={
"budget": 100,
"items": [
{
"name": "Milk 1 L",
"price": 1.49
},
{
"name": "Bread",
"price": 2.25
},
{
"name": "Eggs (12)",
"price": 3.8
},
{
"name": "Apples 1 kg",
"price": 2.99
}
]
},
)
task_id = res.json()["task_id"]<?php
$res = file_get_contents("https://api.kit.forhosting.com/life/shopping-budget", false, stream_context_create([
"http" => [
"method" => "POST",
"header" => "Authorization: Bearer " . getenv("KIT_KEY") . "\r\nContent-Type: application/json",
"content" => '{"budget":100,"items":[{"name":"Milk 1 L","price":1.49},{"name":"Bread","price":2.25},{"name":"Eggs (12)","price":3.8},{"name":"Apples 1 kg","price":2.99}]}',
],
]));
$task = json_decode($res, true);body := bytes.NewBufferString(`{"budget":100,"items":[{"name":"Milk 1 L","price":1.49},{"name":"Bread","price":2.25},{"name":"Eggs (12)","price":3.8},{"name":"Apples 1 kg","price":2.99}]}`)
req, _ := http.NewRequest("POST", "https://api.kit.forhosting.com/life/shopping-budget", body)
req.Header.Set("Authorization", "Bearer "+os.Getenv("KIT_KEY"))
req.Header.Set("Content-Type", "application/json")
res, _ := http.DefaultClient.Do(req)Example request
{
"budget": 100,
"items": [
{
"name": "Milk 1 L",
"price": 1.49
},
{
"name": "Bread",
"price": 2.25
},
{
"name": "Eggs (12)",
"price": 3.8
},
{
"name": "Apples 1 kg",
"price": 2.99
}
]
}Example response
{
"task_id": "tsk_a1b2c3d4e5f6a1b2c3d4e5f6",
"type": "life.shopping_budget",
"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
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
How remaining funds and over-budget status are computed
The endpoint also reports percent of budget used when the budget is greater than zero, so a thirty-dollar cart on a hundred-dollar allowance shows thirty percent used rather than forcing clients to recompute ratios. Rounding is fixed to twelve decimal places for money fields so browser and API goldens stay byte-stable across runtimes without floating noise on simple sums.
Input contract, response shape, and error behaviour
Each line may be a bare number treated as price, or an object with price required and name optional. Lists longer than five hundred lines are rejected to keep pure-parse work bounded. POST a JSON body with two required fields: budget, a finite number greater than or equal to zero, and items, a non-empty array of cart lines. Price also accepts common aliases such as cost or amount; the list field itself accepts aliases cart, prices, lines, and list. Budget accepts aliases limit, max, total_budget, and allowance so scripts can reuse vocabulary from other money tools. On success the body echoes the budget, the item count, each line with a stable name, rounded price, and running remaining after that line, plus total_spent, remaining, over_budget, over_amount, within_budget, percent_used, a short formula string, a human message, and ordered steps for worksheets. Example: budget one hundred with milk at one point four nine, bread at two point two five, eggs at three point eight, and apples at two point nine nine yields total spent ten point five three and remaining eighty-nine point four seven with over_budget false. If the same budget is paired with lines that sum past one hundred, over_budget is true and over_amount shows how far past the limit you went—still a successful response, not an error, because exceeding the budget is the question the tracker answers. Missing budget, empty items, non-finite numbers, or negative prices fail with invalid_input naming the field and are not billed.
Where a shopping budget tracker earns its keep
Household apps and shared grocery lists use a shopping budget tracker so roommates can watch remaining funds as items are ticked off without opening a spreadsheet. Retail demo kiosks and POS training sandboxes need a deterministic remaining-funds oracle that never calls live pricing APIs. Keep requests small, pin rounded totals in tests, and you get reproducible remaining funds for mobile checklists, LMS plugins, and edge workers without standing up ledger infrastructure of your own. Personal finance courses assign cart-versus-budget exercises; an API with ordered running remaining after each line lets graders mark which addition first went over. Automation scripts that build weekly meal plans can post ingredient line totals and halt restock orders when over_budget flips true.
Integration use cases
Meal-plan automation
Scripts send planned ingredient prices against a fixed allowance and halt restock when over_budget becomes true.
Technical questions
What does the shopping budget tracker cost?
The browser tool is free. API requests use prepaid KIT balance at $0.002 per successful call; invalid input is not billed.