Free Tools for Smarter Shopping
Instant tools for percent off, sales tax, unit price, and stacked discounts. No sign-up, mobile-first, always free.
Pick a Tool
Every tool below opens in your browser and returns results as you type. New calculators appear here automatically when published with Parent » Tools.
Which calculator should you use?
Most checkout questions fall into one of three categories. Match the question on your screen to the tool that answers it.
You see a percentage and want the final price
Use a percent-off discount calculator. Enter the original price and the percent off; it returns what you save and what you pay. Right for tag prices, coupon banners, and "extra 20% off" emails.
You see a sticker price and want the total with tax
Use a sales tax calculator. Enter the price and your state's tax rate; it returns the tax amount and the out-the-door total. Right for big-ticket buys where the receipt total is what matters.
You see two pack sizes and want the better deal
Use a unit price calculator. Enter the price and size of each option; it returns the cost per ounce, pound, or unit and points out the winner. Right for groceries, household supplies, and bulk-vs-small comparisons.
The math behind these calculators
Every formula on FatSaver is plain arithmetic. Use this cheat sheet to sanity-check any answer or do the math in your head when you're offline.
Final Price = Original Price × (1 − Discount % ÷ 100)
Example: 30% off $70 = $70 × 0.70 = $49.
Total = Price × (1 + Tax Rate % ÷ 100)
Example: $100 at 7% tax = $100 × 1.07 = $107.
Unit Price = Total Price ÷ Quantity
Always compare in the same unit (oz vs oz, lb vs lb).
Final = Price × (1 − d1) × (1 − d2)
20% + 30% stacked = 44% off, not 50%. Each discount applies to an already-reduced price.
Pair the math with a real offer
A calculator tells you what a discount is worth. A live offer is how you actually pay that lower price. Open a tool, then check FatSaver for verified deals to stack on top of the percent off you just calculated.
Common questions about FatSaver tools
Are FatSaver's calculators free to use?
Yes. Every calculator on this page is free, runs entirely in your browser, and never asks you to sign up or share an email. There are no usage limits and no paid tier.
Do these tools work on a phone?
Yes. Each tool is built mobile-first with large touch targets and number-only keypads, so you can run the math at a checkout aisle or in the car. Results appear instantly as you type.
Are the answers accurate enough for real purchases?
Yes. The tools use standard arithmetic, round only the final displayed value, and show the formula alongside the result so you can verify the math.
Why does a 20% + 30% double discount not equal 50% off?
Because the second discount applies to the already-reduced price. 20% off $100 leaves $80; another 30% off $80 leaves $56. The effective discount is 44%, not 50%.
How often is the tool list updated?
New calculators are added when readers ask for them. The list above is generated automatically from published tool pages, so what you see is always current.
