Unit price comparison calculator
A 32-ounce jar at 5.99 beats a 16-ounce jar at 3.49 once both prices are divided by size: it costs less per ounce. Enter shelf prices and package sizes in one unit and the best value is flagged for you. Free in your browser.
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- Your data stays on your device
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Runs in your browser. Free, unlimited — your data never leaves this page.
A unit price comparison calculator turns shelf prices and package sizes into a fair per-unit ranking so you can see which product is actually cheaper. Enter two or more products with a total price and a package size in the same unit—ounces, milliliters, grams, or count—and the tool returns price divided by size for every line, flags the best value as the lowest unit price, and shows step-by-step arithmetic you can trust in a homework check, a grocery app, or a procurement spreadsheet.
What unit price means when packages differ
Unit price is the total shelf price divided by the amount you actually get: ounces in a jar, milliliters in a bottle, grams in a bag, or pieces in a multipack. When Brand A costs three dollars forty-nine for sixteen ounces and Brand B costs five dollars ninety-nine for thirty-two ounces, comparing the shelf totals alone is misleading—one jar is smaller. Dividing each price by its size yields a common denominator so you can rank true cost per ounce, per milliliter, or per sheet.
The best value is the product with the lowest unit price, not necessarily the lowest sticker or the largest package. Bulk is often cheaper per unit, but not always: a sale on a small pack can undercut a warehouse club size, and multipacks sometimes hide a higher unit rate than the single. This calculator does not convert units for you—if one product is in fluid ounces and another is in liters, convert to one size unit first—nor does it apply tax, coupons, membership fees, or loyalty discounts.
It only applies the arithmetic you already use by hand: unit price equals price over size, then pick the minimum. Teachers of consumer math, budget coaches, and product managers who ship “which is cheaper?” widgets all need that same deterministic contract: same inputs, same unit prices, same best-value flag, every environment.
Zero and negative sizes are hard errors because division by zero is undefined and a negative package size is not a physical quantity in this model.
Practical tips, limits, and related searches
Use the same size unit for every product in a single call: mixing ounces with milliliters without converting will not be fixed for you and will produce a meaningless ranking. Prefer sending numbers rather than currency-formatted strings; string numbers are accepted only when they match a strict finite numeric pattern without dollar signs or commas. Keep price non-negative—free samples at price zero are allowed and yield zero unit price—while size must stay strictly positive.
Prefer this capability when you already know shelf price and package size and only need unit price plus best-value selection; if your source is a receipt photo, extract those numbers first.
What you can do with it
Grocery aisle best-value check
Shoppers enter two or more shelf prices and package sizes and buy the option with the lowest unit price instead of the lowest sticker.
Consumer-math homework and worksheets
Students compare multipacks versus singles and verify hand-written unit prices and best-value choices against a deterministic result.
FAQ
How is unit price calculated?
The best value is the product with the lowest unit price when all sizes use the same unit.
How many products can I compare?
Each product needs a non-negative price and a strictly positive size.
Is the unit price comparison calculator free?
The browser tool is free and runs locally.
Is the bigger package always the better deal?
No. Bulk is often cheaper per unit, but a sale on a small pack can undercut a warehouse size, and multipacks sometimes hide a higher unit rate than the single item. Only the price per unit settles it.
Can I compare ounces with milliliters?
Not directly. Convert every product to the same size unit first, because the calculator does not convert units for you. Mixing ounces with milliliters would give a ranking that means nothing.
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/unit-price \
-H "Authorization: Bearer $KIT_KEY" \
-H "Content-Type: application/json" \
-d '{"products":[{"name":"Brand A 16 oz","price":3.49,"size":16},{"name":"Brand B 32 oz","price":5.99,"size":32}]}'const res = await fetch("https://api.kit.forhosting.com/life/unit-price", {
method: "POST",
headers: {
"Authorization": `Bearer ${process.env.KIT_KEY}`,
"Content-Type": "application/json"
},
body: JSON.stringify({
"products": [
{
"name": "Brand A 16 oz",
"price": 3.49,
"size": 16
},
{
"name": "Brand B 32 oz",
"price": 5.99,
"size": 32
}
]
})
});
const { task_id } = await res.json();import os, requests
res = requests.post(
"https://api.kit.forhosting.com/life/unit-price",
headers={"Authorization": f"Bearer {os.environ['KIT_KEY']}"},
json={
"products": [
{
"name": "Brand A 16 oz",
"price": 3.49,
"size": 16
},
{
"name": "Brand B 32 oz",
"price": 5.99,
"size": 32
}
]
},
)
task_id = res.json()["task_id"]<?php
$res = file_get_contents("https://api.kit.forhosting.com/life/unit-price", false, stream_context_create([
"http" => [
"method" => "POST",
"header" => "Authorization: Bearer " . getenv("KIT_KEY") . "\r\nContent-Type: application/json",
"content" => '{"products":[{"name":"Brand A 16 oz","price":3.49,"size":16},{"name":"Brand B 32 oz","price":5.99,"size":32}]}',
],
]));
$task = json_decode($res, true);body := bytes.NewBufferString(`{"products":[{"name":"Brand A 16 oz","price":3.49,"size":16},{"name":"Brand B 32 oz","price":5.99,"size":32}]}`)
req, _ := http.NewRequest("POST", "https://api.kit.forhosting.com/life/unit-price", body)
req.Header.Set("Authorization", "Bearer "+os.Getenv("KIT_KEY"))
req.Header.Set("Content-Type", "application/json")
res, _ := http.DefaultClient.Do(req)Example request
{
"products": [
{
"name": "Brand A 16 oz",
"price": 3.49,
"size": 16
},
{
"name": "Brand B 32 oz",
"price": 5.99,
"size": 32
}
]
}Example response
{
"task_id": "tsk_a1b2c3d4e5f6a1b2c3d4e5f6",
"type": "life.unit_price",
"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.
Limits
min_products | 2 |
max_products | 50 |
max_abs | 1000000000000 |
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
Zero or negative package sizes are rejected with invalid_input instead of inventing infinity or a nonsense bargain.
How to call the API and what comes back
You may also send parallel arrays prices and sizes of equal length, with optional names or labels. Send a JSON body with one required field: products (aliases items, options, list), an array of at least two and at most fifty objects. Each object needs a finite non-negative price (aliases cost, amount) and a strictly positive size (aliases quantity, qty, units, package_size). Optional name (aliases label, title) labels the line in the response; when omitted the tool uses Product 1, Product 2, and so on. Absolute values for price and size must stay within one trillion so intermediate quotients remain finite in IEEE double precision on the Worker and in the browser. On success the response sets count to the number of products compared, products to an array of objects each with index, name, rounded price and size, unit_price, and is_best_value, best_index to the first index with the lowest unit price, best_name, best_unit_price, best_price, and best_size to that winner’s fields, savings_vs_worst_per_unit to the gap between the highest and lowest unit price, formula to the string unit_price equals price over size, message to a short English summary, and steps to an ordered array of substitution lines. Failed validation—missing products, fewer than two items, non-finite numbers, values outside absolute limits, or any size that is zero or negative—returns invalid_input and is never charged. Pricing is a flat $0.002 per successful request with unit item and zero marginal unit price.
Practical tips, limits, and related searches
When teaching, pair examples: three point four nine for sixteen ounces versus five point nine nine for thirty-two ounces shows the larger pack winning on unit price; a sale that drops the small pack below the bulk unit rate shows best value flipping; two products with identical unit prices produce a documented tie with both is_best_value true and best_index pointing at the first; and a size of zero or a negative size demonstrates the hard invalid_input path. This landing targets people searching for a unit price comparison calculator, price per unit tool, or best value package size checker; it is not a live grocery scraper, not a multi-currency converter, and not a coupon optimizer. Failed tasks that return invalid_input do not consume prepaid balance, which keeps exploratory scripts cheap when learners deliberately set size to zero. Round-trip checks are easy: recompute each price divided by size by hand and confirm it equals the published unit_price within the same twelve-decimal rounding, and confirm that the product with the minimum unit_price is the only one flagged as best value unless a true tie exists.
Integration use cases
Procurement and catalog unit tests
Teams batch-evaluate SKU price and pack size pairs and assert best_index and unit_price fields in checkout or catalog UI tests.
Technical questions
What happens if package size is zero or negative?
The tool returns invalid_input. A zero or negative size cannot define a meaningful unit price, so the request is rejected and not charged.
What if two products have the same unit price?
Both are flagged is_best_value true. best_index points to the first product that achieved the minimum unit price.