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Percentages in daily life: discounts, marks, GST and salary hikes

By the FreeAllTool team · Published November 27, 2025

Percentages appear everywhere: shop discounts, exam results, GST on bills, interest rates and salary hikes. Most of these problems use one of just three formulas. Once you know which one fits, the maths is quick.

The three basic formulas

  • Finding a percentage of a number: number × percent ÷ 100.
  • Finding what percent one number is of another: part ÷ whole × 100.
  • Finding percentage change: (new − old) ÷ old × 100.

Shopping discounts

A shirt costs ₹1,499 with 30% off. The discount is 1,499 × 30 ÷ 100 = ₹449.70, so you pay about ₹1,049. A faster way is to multiply by the share you actually pay: 70% of ₹1,499 is 1,499 × 0.70 = ₹1,049.30.

Watch out for “extra” discounts. “40% off plus an extra 10%” is not 50% off. The extra 10% applies to the already reduced price, so the total discount is 46%.

Exam marks

If you scored 437 out of 600, your percentage is 437 ÷ 600 × 100 = 72.83%. To find how many marks you need for a target, reverse the formula: for 75% of 600, you need 600 × 75 ÷ 100 = 450 marks.

GST on a bill

If a service costs ₹5,000 before tax and GST is 18%, the tax is 5,000 × 18 ÷ 100 = ₹900, making the total ₹5,900. If you only know the final amount including GST and want the original price, divide by 1 plus the rate: 5,900 ÷ 1.18 = ₹5,000. Subtracting 18% from ₹5,900 would give the wrong answer, because the tax was calculated on the smaller amount.

Salary hikes

Your monthly salary rises from ₹42,000 to ₹46,200. The hike is (46,200 − 42,000) ÷ 42,000 × 100 = 10%. Comparing offers this way helps you see which raise is really bigger.

Percentage points versus percent

If a bank’s interest rate goes from 6% to 7%, it has risen by one percentage point, but by about 16.7% in relative terms. News reports sometimes mix these up, so it is worth checking which one is meant.

Do it in seconds

Our percentage calculator solves all three types of problems instantly. Try the examples above to check your understanding.

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