Enter each product's price and size. The calculator converts everything to the same unit, ranks up to 8 products from lowest to highest unit price, and shows what the gap adds up to over a year.
This tool runs entirely in your browser. What you enter is never sent anywhere.Your input is never sent anywhere.
DetailsExamples use sample sizes and prices. Replace them with the numbers from your shelf tags.
Lowest unit price
Large bottle, 28 fl oz
$0.356per fl oz
Unit price
Keep in mind
Unit price is the price divided by the total quantity, where total quantity is the size of one item times the number of items in the pack. Enter the pack count for multipacks. Prices are used as typed, with no sales tax added, so enter every price the same way. A lower unit price can still cost more if you use more of the product, it expires first, or it takes space you do not have.
Products to compare (3)
Total 12.6 fl oz · $0.474 per fl oz
Total 28 fl oz · $0.356 per fl oz
Total 25.2 fl oz · $0.434 per fl oz
Compare up to 8 products. Your entries are saved in this browser only and restored on your next visit. They are not sent to a server.
How to Calculate Unit Price for Products in Different Sizes
Shelf prices are hard to compare because every package is sized differently. A 1-gallon jug, a 64 fl oz jug and a 12-pack of 16 fl oz bottles cannot be judged by the price tag alone.
The math is simple: divide the price by the total quantity. Total quantity is the size of one item times the number of items in the pack. This calculator does the conversions for you. Pick a unit type, choose the unit printed on each label (fl oz, qt, gal, mL, L, oz, lb, g, kg, ft, yd, sq ft and more), and it shows every product at the same price basis, such as per fl oz, per quart, per lb or per 100 sheets. Up to 8 products are ranked from the lowest unit price to the highest.
Add how much you use, per day, week or month, and the tool also shows the cost per day, per month and per year, plus how long one package lasts. A few cents of difference per ounce can turn into a real dollar amount over a year, and you can set a different usage for each product to test whether a big package makes you use more.
Everything is calculated in your browser, and the numbers you enter are not sent to a server. They are saved in this browser so you can pick up where you left off.
Everyday Shopping Decisions This Settles
Bulk size or regular size
Put a 28 fl oz bottle next to two 12.6 fl oz bottles, or a 5 lb bag next to a 12 oz bag, and see which one costs less per fl oz or per oz.
Refill pouch or original container
Enter the container and the refill side by side. The percentage gap shows whether the refill is actually cheaper, including when a sale or bonus-size bottle changes the answer.
Multipacks and club-store packs
Use the Items in pack field for 3-packs, 12-packs and 36-packs. The total quantity is worked out for you, so a bigger count is not mistaken for a better deal.
Toilet paper and paper towels
Compare total sheets, or total square feet for paper towels and foil, instead of roll names that mean different things from brand to brand.
Detergent and pods by the load
Switch to Count, set the unit to loads, and compare liquid and pods on a price-per-load basis. Cross-check with price per fl oz for the liquids.
Recurring purchases in your budget
Enter how much you use per day, week or month to see a yearly cost for each option, and how many months one package lasts.
How to Compare Two or More Products
- Pick a unit type: Volume, Weight, Count, Length or Area. You can also start from an example such as Shampoo or Toilet paper.
- Under "Show price", choose the basis for the results, for example per fl oz, per quart, per lb or per 100 sheets.
- For each product, enter a name, the price, the number of items in the pack, the size of one item, and its unit.
- Use "Add product" to compare up to 8 products. Results update as you type.
- Read the ranking. The lowest unit price is on top, and every other product shows how much more it costs.
- Open the "Usage & yearly cost" tab, pick Per day, Per week or Per month, and enter how much you use. You get the cost per day, month and year and how long one package lasts.
- Press "Copy results" to paste the comparison into a note or message.
Note: There is no calculate button. Your entries are saved in this browser's local storage and restored on your next visit.
How the Math Works and What to Check
- Formula: unit price = price ÷ total quantity. Total quantity = size of one item × items in pack, converted to a common unit.
- Pack count: if "Items in pack" is empty or 0, it is treated as 1.
- Conversions: 1 gal = 128 U.S. fl oz, 1 qt = 32 fl oz, 1 pt = 16 fl oz, 1 L ≈ 33.8 fl oz, 1 lb = 16 oz, 1 kg ≈ 35.3 oz, 1 yd = 3 ft, 1 sq yd = 9 sq ft.
- Volume and weight are separate. fl oz measures volume and oz measures weight, and the calculator does not convert between the two.
- Yearly cost = cost per day × 365. Monthly cost uses 365 ÷ 12 days. "Lasts" is the total quantity of the whole package divided by your daily usage, so it is an estimate.
- Usage is entered in the base unit of the group: fl oz, oz, ft, sq ft, or the counting unit (sheets, loads and so on). The usage period is converted to a daily amount.
- Prices are used as typed. No sales tax, coupon or discount is added, so enter the price you would actually pay.
- The Reset button replaces your entries, and the saved copy, with the sample data.
Worked Examples: Price per Fl Oz, per Load and per 100 Sheets
Each row shows which unit to use and how the unit price is worked out. The numbers match what you would enter in the calculator.
| Item | Compare by | Example math | What to watch for |
|---|---|---|---|
| Shampoo | Price per fl oz | $5.97 ÷ 12.6 fl oz = $0.474 | Compare refills and bottles in the same unit. |
| Laundry detergent | Price per load | $11.97 ÷ 64 loads = $0.187 | Each brand sets its own dose per load. Also check price per fl oz. |
| Toilet paper | Price per 100 sheets | $14.97 ÷ (12 rolls × 330 sheets) × 100 = $0.378 | Use total sheets. Roll names are not standard. |
| Paper towels | Price per 100 sheets | $9.97 ÷ (6 rolls × 78 sheets) × 100 = $2.13 | Sheet size varies. Use sq ft if the pack lists it. |
| Aluminum foil | Price per sq ft | $4.47 ÷ 75 sq ft = $0.0596 | Same length can mean a different width. Compare area. |
| Vitamins | Price per tablet | $19.99 ÷ 120 tablets = $0.167 | Check how many tablets are in one serving. |
| Coffee | Price per oz | $21.99 ÷ (2 lb × 16 oz) = $0.687 | Convert lb to oz first. A big bag only helps if you finish it while fresh. |
Is the Bigger Package Really Cheaper? What to Check Beyond the Unit Price
Unit price is where the decision starts. These points cover the cases where it can still lead you wrong.
Short answer: divide by total quantity, then compare in one unit
The calculation is one line: price ÷ total quantity. The hard part is getting every product into the same unit.
Example: a 2-pack of 12.6 fl oz shampoo for $10.94 holds 25.2 fl oz, which is about $0.434 per fl oz. A single 28 fl oz bottle for $9.97 comes to about $0.356 per fl oz. The single large bottle is cheaper per fl oz, even though the 2-pack has more individual bottles.
Judge by the unit price, not by the package count or the size on the front.
Three mix-ups that skew a comparison
1. Mixed units. A 1-gallon jug and a 64 fl oz jug are not 1 versus 64. One gallon is 128 fl oz, so the gallon jug is twice the size.
2. Fluid ounces versus ounces. fl oz measures volume and oz measures weight. Compare products by the same kind of unit.
3. A forgotten pack count. A 3-pack of 16 fl oz bottles is 48 fl oz, not 16.
This calculator keeps the unit types separate, converts within each type, and asks for the pack count as its own field.
Refill or original container: which is cheaper per fl oz?
A refill skips the container, so it often costs less per fl oz. It is not guaranteed. A sale on the original, a bonus-size bottle, or a refill that only comes in a small size can flip the result.
Enter both and read the percentage gap. If the difference is small, the more convenient option may be the better choice.
Toilet paper and paper towels: compare sheets or area, not rolls
Roll names such as Mega, Double or Family are marketing terms. They can mean different sheet counts from one brand to the next, so a 12-roll pack and a 24-roll pack are not comparable until you multiply out the sheets.
For paper towels, sheet size also varies. If the package lists total square feet, use the Area group and compare the price per sq ft. If it does not, compare price per 100 sheets and keep in mind that the sheets may differ in size.
When the lowest unit price is not the best buy
1. You use more. A large container can lead to bigger pours. If the unit price is 10% lower but you use 20% more, you spend more. Turn off "Use the same usage for every product" and test it.
2. It expires or goes stale first. Check the "Lasts" estimate in the yearly tab. If it runs past the date on the package, a smaller size may be the better value.
3. Storage and cash. A 24-pack takes space, and paying for months of supply up front ties up money. If the yearly gap is small, you may prefer the smaller pack.
Turn small differences into dollars per year
A unit price like $0.474 versus $0.356 per fl oz is hard to judge. Add how much you use and it becomes concrete.
Example: at an assumed 0.2 fl oz of shampoo per day, the first option comes to roughly $35 a year and the second roughly $26, a gap of about $9. For an item you use rarely, the same percentage gap may be only a few cents a year. The yearly view helps you decide which items are worth comparing carefully.
Enter the price you actually pay
Shelf price is not always your price. If a coupon, store loyalty price or subscription discount applies, enter the price after that discount. The calculator does not add sales tax, so apply the same approach to every product.
Common Mistakes When Comparing Sizes and Multipacks
Forgetting the pack count
A 3-pack of 16 fl oz bottles costs $11.97. Entered as a single 16 fl oz item, it looks like $0.748 per fl oz. The real total is 48 fl oz, or about $0.249 per fl oz.
💡 See the solution▼
Comparing a gallon and a half-gallon by sticker price
A 1-gallon jug at $3.99 looks more expensive than a 64 fl oz jug at $2.29, but it holds twice as much. Per fl oz, the gallon is about $0.0312 and the smaller jug is about $0.0358.
💡 See the solution▼
Mixing volume and weight
A liquid sold by fl oz and a product sold by oz measure different things. Treating them as the same unit gives a number that has no meaning.
💡 See the solution▼
Judging toilet paper by roll count
A pack of 24 rolls with 190 sheets each has 4,560 sheets, about 15% more than 12 rolls with 330 sheets each (3,960 sheets). Yet at $18.97 versus $14.97, the 24-roll pack costs about $0.416 per 100 sheets against $0.378.
💡 See the solution▼
Using more because the container is bigger
A large bottle can lead to bigger pours. A lower unit price stops mattering if the extra use outweighs the savings.
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Buying more than you can finish
A very large size of coffee, vitamins or cooking oil can pass its date or go stale before you use it, and the savings go in the trash.
💡 See the solution▼
Questions About Bulk Pricing, Refills and Multipacks
Q.How do you calculate unit price?
A. Divide the price by the total quantity. The total quantity is the size of one item times the number of items in the pack. For example, a 2-pack of 12.6 fl oz bottles for $10.94 holds 25.2 fl oz in total, so the unit price is $10.94 ÷ 25.2 = about $0.434 per fl oz. To compare it with other products, show every price in the same unit, such as per fl oz, per quart or per 100 sheets.
Q.How do I compare products sold in different sizes or units, like gallons, quarts and ounces?
A. Choose the unit type (Volume, Weight, Count, Length or Area), then pick the unit printed on each label. The calculator converts everything with standard factors before it divides: 1 gallon is 128 U.S. fluid ounces, 1 quart is 32, 1 liter is about 33.8, and 1 pound is 16 ounces. A 1-gallon jug and a 64 fl oz jug can sit side by side in the same comparison.
Q.Is the bigger package always cheaper per ounce?
A. No. Larger sizes often have a lower unit price, but not every time. A sale on the smaller size, a bonus-size bottle, or a multipack priced oddly can reverse it. Enter both and compare the unit prices instead of assuming. Even when the large size is cheaper per ounce, it only saves money if you use it up before it expires or loses freshness.
Q.How do I compare toilet paper and paper towels?
A. Compare total sheets, not roll counts. Roll names such as Mega or Double are marketing terms and can mean different sheet counts from one brand to the next. Choose Count, set the unit to sheets, enter the sheets per roll and the number of rolls, and show the price per 100 sheets. For paper towels, sheet size also varies, so if the package lists total square feet, use the Area group and compare the price per sq ft.
Q.How can I compare laundry detergent when one is liquid and one is pods?
A. Use price per load. Choose Count, set the unit to loads, and enter the load count from the label. Each brand sets its own dose per load, so also run a second comparison in Volume (price per fl oz) for the liquids. If the two views disagree, trust the one that matches how much you actually pour.
Q.How do I estimate how much I use?
A. Start with the label: detergent caps, serving sizes and dosing lines show the amount per use. Otherwise, track one package. Write down the day you open it and the day it runs out, then divide its size by the number of days. If you count uses instead, such as four loads a week, enter 4 and switch the usage period to Per week. The calculator turns that into a daily figure.
Q.Does it handle multipacks like a 3-pack?
A. Yes. Enter the size of one item in the "Size of one item" field and the number of items in "Items in pack". A 3-pack of 16 fl oz bottles is 48 fl oz in total. If you leave the pack count empty or enter 0, the calculator treats it as 1.
Q.How many products can I compare at once?
A. Up to 8. Products with a price and size are ranked from the lowest to the highest unit price, and the lowest one is marked with a crown. Each of the others shows how many percent more it costs than the lowest.
Q.Are my entries saved or sent anywhere?
A. The calculation runs in your browser, and the numbers you type are not sent to a server. Your entries are saved in this browser's local storage so they are still there on your next visit. The Reset button replaces your entries, and the saved copy, with the sample data.
Q.Can I use it in the store with a weak signal?
A. Once the page has loaded, every calculation happens on your device, so entering numbers and reading results does not need a connection. You do need a connection to open the page in the first place.
Q.Does the calculator add sales tax?
A. No. It uses the prices exactly as you type them. Shelf prices in the U.S. usually do not include sales tax, so enter every price on the same basis. If a coupon, loyalty price or subscription discount applies, enter the price you would actually pay.
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