Price Comparison Calculator — Cheapest Price per Unit

Quick Start Guide

  1. Add your first item: Name it, then enter its price and quantity (e.g., $5.00 for 10 oz).
  2. Add more items: Click "Add Item" for every other price or package size you want to compare.
  3. Pick a category and unit: Weight, Volume, Length, Area, Quantity, Data, Energy, or Time — the calculator converts every item to one unit within that category automatically.
  4. View the verdict: See which item is cheaper per unit, plus the percentage and dollar amount saved.
  5. Adjust for discounts, tax, or waste (optional): Switch to Discount & Tax or Real Cost mode when a coupon, sales tax, or usable yield should factor into the comparison.
  6. Export your results: Save the comparison to JSON or CSV.

Understanding Price Comparison

What is unit price?

Unit price is what one standard amount costs — per gram, per ounce, per litre, per item. You get it by dividing the package price by its size: a $4.99 pack of 500 g works out to about $0.01 per gram. Comparing unit prices, rather than sticker prices, tells you which option is genuinely the better deal.

How to tell which is cheaper

Look at the price per unit, not the total price. A bigger box usually costs more overall but can be cheaper per unit — or not. Enter each product’s price and size and the calculator ranks them, then highlights the lowest unit price as the best deal.

Is the bigger size always the better deal?

No. “Family size” and bulk packs are often — but not always — cheaper per unit. Stores sometimes price the larger size at a higher cost per unit, so the smaller pack wins. The only way to know is to compare the unit price, which is exactly what this tool does.

Comparing different sizes and units

Products rarely come in matching sizes — one is in grams, another in kilograms; one in fluid ounces, another in litres. Pick the unit for each item and the calculator converts everything to a common unit first, so the comparison is fair. It also handles length, area, quantity, data (per GB), and energy (per kWh).

When discounts, tax, and waste change the answer

Switch to Discount & Tax mode to apply a coupon or sale and add sales tax to each item before ranking — a discount can flip which option is cheapest. Real Cost mode goes further: if part of a package is wasted (trimmed, spoiled, unusable), enter the usable yield, or a serving count, to compare the true cost of what you actually use.

Common mistakes to avoid

Judging by the sticker price instead of the price per unit; comparing mismatched units (grams against ounces) without converting; and ignoring waste on fresh food, where a cheaper package can cost more per usable portion. Comparing on a single common unit avoids all three.

Features

Compare any number of items: Add as many products or package sizes as you like — the cheapest per unit is highlighted automatically.

Any size, any unit: Mix grams and kilograms, ounces and litres, packs and pieces — everything is converted to one unit for a fair comparison. Beyond weight and volume, also compare by length, area, data storage, energy, or time (hourly, monthly, and yearly rates).

See your savings: Get the price gap versus the next-best option, plus projected monthly and yearly savings.

Go deeper when it matters: Optional discount and tax adjustments, or real cost per usable portion — then copy or export the comparison.

Common Use Cases

Is the bigger size cheaper?: check whether "family size" really beats the regular pack and see the true cost per unit at a glance.

Compare brands & stores: weigh a brand vs store-brand, or the same item at two shops, and compare a sale price against the regular size.

Bulk & warehouse clubs: confirm a multi-pack really saves per unit and justify (or skip) the bulk purchase.

Sold by count, not size: check a 6-pack against a dozen, or price per piece against a pack, for eggs, batteries, and anything else priced by the item.

Beyond groceries: compare cloud storage per GB, electricity per kWh, materials per metre or square yard, or anything priced by size or amount.

Subscriptions & rentals: compare monthly vs yearly plan pricing, a daily vs weekly rental rate, or hourly freelance/labor rates on an even footing.

Frequently Asked Questions

Compare the price per unit, not the total price. Enter each product’s price and size and the calculator works out the cost per unit for each, then highlights the lowest one as the best deal. A cheaper sticker price often loses once you account for how much you actually get.
No. Larger and "family size" packs are usually — but not always — cheaper per unit. Some stores price the bigger size at a higher cost per unit, so the smaller pack wins. The only reliable way to tell is to compare the unit price, which is what this calculator does.
Unit price = total price ÷ quantity. For example, a 500 g pack at $3.00 has a unit price of $0.006 per gram. The calculator applies this to every item and normalises the units, so you can compare grams vs kilograms, ounces vs pounds, and so on.
Yes. Choose a Category — Weight, Volume, Length, Area, Quantity, Data, Energy, or Time — and the unit for each item within it (grams vs kilograms, ounces vs pounds, US vs UK pints, square feet vs square yards, and so on). The calculator converts everything to a common unit before ranking, so the comparison is fair even when the sizes or units do not match.
Yes — select the Time category to compare anything priced per minute, hour, day, week, month, or year: a monthly vs. annual subscription, an hourly freelance or labor rate, or a daily vs. weekly rental. The calculator converts every price to the same time unit (e.g. dollars per month) before ranking, the same way it does for groceries.
Simple mode compares the plain price per unit. Discount & Tax mode applies a coupon or sale and adds sales tax to each item before ranking, which can flip the winner. Real Cost mode goes further, adjusting for usable yield or serving count so you compare the true cost of what you actually use — useful for fresh food that gets trimmed or wasted.
When at least two valid items are entered, the calculator estimates the saving between the best and next-best option, then projects monthly and yearly savings using how often you say you buy per month.

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