Discount & Cashback Calculator

[PLEASE READ FIRST] This app shows no shop information and no coupons. It keeps no record of what you buy. You type numbers and it does the arithmetic. ────────── 🧮 Discount & Cashback Calculator — discounts do not add up Twenty percent off, and then another ten percent off. That is not thirty percent off. It is twenty-eight. What is left is 0.8 x 0.9 = 0.72, so 72 percent of the price remains. Discounts multiply, so the real figure is always smaller than the sum. 10 and 10 -> 19% off (adding gives 20%) 20 and 10 -> 28% off (adding gives 30%) 30 and 20 -> 44% off (adding gives 50%) 50 and 50 -> 75% off (adding gives 100%) Half off twice does not make it free. It stops at 75 percent off. Half of a half is a quarter, so a quarter of the price is still there. ■ And another thing. "10% cashback" is not "10% off" Cashback is money you can spend next time, so it does not reduce what you hand over today. Pay 1000 and get 100 back, and you have bought 1100 worth of goods for 1000. That is 1000 divided by 1100 — an effective 9.090909 percent off, weaker than 10 percent off. The gap widens as the rate goes up. 20 percent cashback is only 16.66667 percent off, and even 100 percent cashback comes to half price and no further. ■ Four topics ▪ Stacked … a price and two percentages. Gives what you pay and the total percent off ▪ Order … a price, a percentage and a fixed amount off. Both orders, side by side ▪ Cashback … type a rate, and read the discount it is really worth ▪ What percent off … the original price and what you paid. Gives the rate and the amount taken off ■ The app never asks which order came first If someone asks you whether the percentage or the fixed amount went on first and you can answer, you are already past the part that trips people up. Type the numbers and both readings appear. 5000, with 20% off and 1000 off percent off, then fixed: 3000 fixed off, then percent: 3200 The gap is 200, and taking the percentage off first is the cheaper one. A percentage applies to whatever the price is at that moment, so taking the fixed amount off first leaves the percentage a smaller number to work on. ■ No currency symbol A discount works the same way in every currency, so this app handles numbers only. Type a price from anywhere and it behaves the same. ■ What the screen holds ▪ Four topics, one to three input fields. No settings screen ▪ Common values are one tap away ▪ The last five entries stay in the history ▪ A quick chart and a reverse lookup on the cashback topic ▪ Six short notes ▪ Japanese and English, chosen by your device language ■ What this app does not do ▪ It shows nothing that comes from a shop ▪ It keeps no record of what you buy ▪ It does not work out tax ▪ It holds no expiry dates and no rules for any particular card ▪ It does not calculate instalments or interest No account is needed. The calculation happens on your device, and nothing you type is sent out. ────────── For working out what the label on the shelf really comes to, and for checking a percentage while you are still standing in front of it.