Percentages appear in prices, taxes, marks, salaries and discounts. A few formulas cover almost every case. Here they are, with examples you can check with a calculator.
1. What is X% of a number?
Amount = number × X ÷ 100. Example: 15% of Rs 8,000 = 8,000 × 15 ÷ 100 = Rs 1,200.
2. What percentage is one number of another?
Percentage = part ÷ whole × 100. Example: you scored 42 out of 60, so 42 ÷ 60 × 100 = 70%.
3. Price after a discount
New price = price × (1 − discount ÷ 100). Example: a Rs 8,500 jacket with 20% off costs 8,500 × 0.80 = Rs 6,800, so you save Rs 1,700.
4. Adding sales tax
Price with tax = price × (1 + tax rate ÷ 100). Example: at an 18% sales tax rate, Rs 6,800 becomes 6,800 × 1.18 = Rs 8,024. The standard sales tax rate in Pakistan is 18% at the time of writing, but some goods have different rates, so check the current rate for your product with FBR or your accountant.
5. Taking tax out of a total
If a bill of Rs 11,800 already includes 18% tax, price before tax = total ÷ 1.18 = Rs 10,000, and the tax is Rs 1,800. A common mistake is to take 18% off the total, which gives the wrong answer.
6. Percentage increase or decrease
Change % = (new − old) ÷ old × 100. Example: a salary goes from Rs 80,000 to Rs 92,000. The change is 12,000 ÷ 80,000 × 100 = a 15% increase.
7. Two discounts are not added together
A 20% discount followed by a further 10% off is not 30%. Apply them one after the other: 100 × 0.80 × 0.90 = 72, a total discount of 28%.
Quick table
| Want | Multiply by |
|---|---|
| Take 10% off | 0.90 |
| Take 25% off | 0.75 |
| Add 18% tax | 1.18 |
| Add 5% increase | 1.05 |
Let the tool do it
Use the free Percentage Calculator for any of these, and see profit margin and markup if you price products for sale.