# Percentage, Margin and ROI Calculators

> Four quick free tools for percentages, sale prices with tax, profit margin, markup and return on investment, with the formula shown for each answer

These 4 free calculators answer everyday questions: what's 15% of a bill, how much is left after a sale, and how much profit sits inside a price. The percentage, discount, profit margin and ROI calculators each show the formula behind the answer, so you can repeat the sum by hand if you don't trust a screen.

## How do I find a percentage or a percent change?

The [percentage calculator](https://tax-services.ca/calculators/math-business/percentage-calculator) handles the usual cases: a percent of a number, one value as a percent of another, a percent change, and adding or subtracting a percent. Comparing two offers? Work out the percentage difference, not the plain difference. A $20 saving on a $50 item is far bigger than a $20 saving on a $500 one, even though the dollar figure looks the same.

## What is the sale price with tax in Canada?

Prices in Canada usually leave out sales tax, so the till total runs higher than the tag. The [discount calculator](https://tax-services.ca/calculators/math-business/discount-calculator) gives the sale price, the amount saved and the final price with tax after one or two discounts, using the rate for your province. To add tax to any other price, use the [GST and HST calculator](https://tax-services.ca/calculators/sales-tax/gst-hst-calculator).

## What is the difference between margin and markup?

Margin divides profit by the selling price, while markup divides it by what the item cost you, so the two percentages never match. A 50% markup gives a 33% margin. The [profit margin and markup calculator](https://tax-services.ca/calculators/math-business/profit-margin-calculator) converts between cost, price and margin, and works backward too: enter the margin you want and it returns the price to charge.

## Is my investment paying off?

The [ROI calculator](https://tax-services.ca/calculators/math-business/roi-calculator) sets a gain or loss against the money you put in. From the amount invested and the ending value, it returns the ROI, the compound yearly return and the payback period. For savings with regular deposits, the [compound interest calculator](https://tax-services.ca/calculators/savings-budget/compound-interest-calculator) fits better.

## All the math and business calculators

The full list sits below. Dollar amounts show to the cent, and rounding follows normal rules.

---
Source: https://tax-services.ca/calculators/math-business
Last updated: 2026-10-01
Independent information site. Not affiliated with the CRA. No services, no guarantee of accuracy. See https://tax-services.ca/disclaimer