2026-07-16
Percentage, Discount, Tip, and ROI — Everyday Math That Pays Off
Four high-traffic calculators explained: when to use percentage math, sale discounts, restaurant tips, and investment ROI.
Most “everyday finance” questions are percentage problems in disguise. The trick is picking the right form of the question.
Percentage calculator: use it for “what is 18% of 240?”, “40 is what percent of 200?”, or “sales went from 80 to 100 — what percent change?”.
Discount calculator: when a store advertises 30% off, you want the sale price and the dollars saved. Working backwards from a sale tag to the original price is equally common.
Tip calculator: restaurant tipping is percentage math plus splitting. Decide tip on the pre-tax bill unless your group agrees otherwise, then divide by the number of people.
ROI calculator: return on investment answers “what did I earn relative to what I put in?” Add a holding period to see annualized ROI so a 3-month flip is not compared naively to a 5-year hold.
Bookmark these four TaskEaser tools for shopping, dining, and quick investment checks — no spreadsheet required.
Related tools
- Percentage Calculator — Find X% of Y, what percent X is of Y, and percentage change
- Discount Calculator — Sale price, savings, and original price from a discount
- Tip Calculator — Calculate tip and split the bill at a restaurant
- ROI Calculator — Return on investment as a percentage and multiple