A tag says 30% off, the cashier mentions an extra 20% at the register, and now you are trying to do the math standing in the aisle. Discount Calculator is an Android app built for exactly that moment. We made a stripped-down version that runs right here: free, no install, no signup. It is called Deal Maths, and it shows your final price the second the page loads.
Use Deal Maths now
It opens on a worked example, 30% off an $80.00 item, so you can see an answer before you touch anything. Slide the discount, tap a preset, or type your own price. If a second discount is stacked on top, switch on the extra discount row.
How to use it
The first tab, Sale price, takes an original price, a discount from 0 to 100%, an optional extra discount, an optional sales tax rate, and a quantity. You get what you pay, what you save, the total discount, and the price per unit. There is no calculate button, and the chart under the total moves as you change anything: grey for the original price, amber for each discount, blue for tax, and indigo for what you pay.
The Original tab runs the math backwards. Enter what you paid and the percentage you were told, and it finds the price before the sale. The % off tab takes two prices and tells you how big the discount really is. Pick your currency symbol at the top, and use Share if you want to send a result.
Then there is the daily quiz. Five short questions, the same set for everyone each day, with a streak that grows when you finish on consecutive days. Your inputs, score, and streak are saved on your device, and nothing leaves your browser.
How it compares to Discount Calculator
Deal Maths keeps the one thing a sale calculator has to get right: you change a number and watch the final price move. It handles a single discount, a stacked second discount, tax, and quantity, and it can work backwards from a sale price. That covers the checkout-line question most people actually have.
What it leaves out is everything that comes from living on your phone. There is no home screen icon, no saved list of past calculations, and no feature set beyond what you see on this page. Rounding follows one fixed rule here, each step to the nearest cent, so a shop that rounds differently can land a cent away from our total.
Our honest advice: use Deal Maths when you are already in a browser, on someone else’s phone, or comparing a few offers at a desk. Install the app if you do sale math every week and want it one tap away.
If you are hunting for the deals themselves rather than the math, our guides to Edadeal alternatives and DealSeek alternatives cover cashback and coupon apps worth a look.
Get the full app
Discount Calculator is free on Android and keeps sale math on your home screen, with no browser tab to find.
Frequently asked questions
How do I calculate a discount?
Multiply the original price by the discount percentage to get the amount off, then subtract it. A 30% discount on $80.00 takes off $24.00 and leaves $56.00. Another way is to multiply the price by 0.70 straight away. Deal Maths does this live as you move the slider.
How do two discounts in a row work?
They multiply, they do not add. Take 30% off, then an extra 20% off the new price, and you pay 70% of 80%, which is 56% of the original. That is 44% off in total, not 50%. Turn on the extra discount row and the Total off figure shows it for you.
How do I find the original price from a sale price?
Divide what you paid by the share of the price you still paid. If you paid $56.00 after 30% off, divide by 0.70 to get $80.00. Adding 30% back onto $56.00 would give $72.80, which is too low. The Original tab handles this step.
Is this discount calculator free, and does it work offline?
Yes, it is free with no signup. Once the page has loaded it keeps working without a connection, and your last inputs are stored in your browser on your device only.
Is this the official Discount Calculator app?
No. Deal Maths is an original tool we built, inspired by the quick sale math that Discount Calculator handles on Android. It is not affiliated with, endorsed by, or connected to the app’s publisher. For the full app, use the store links above.
