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How to Calculate Percentages: X% of Y, Percentage Share and Percentage Change

Quick Answer

X% of Y = X ÷ 100 × Y. "X is what % of Y" = X ÷ Y × 100. Percentage change = (new − old) ÷ old × 100. For example, 20% of Rs 150 is Rs 30, and a price rise from Rs 250 to Rs 300 is a 20% increase.

Overview

Percentages come up daily in Pakistan: a sale discount, a salary increment, a utility bill rise, or a tax rate. This calculator handles the three most common questions with two numbers, X and Y. Choose a mode: - **X% of Y** – e.g. 18% of Rs 10,000. - **X is what % of Y** – e.g. 30 is what percent of 150. - **% change from X to Y** – e.g. salary from Rs 80,000 to Rs 92,000.

How It Works

1. Enter the first number (X). 2. Enter the second number (Y). 3. Pick the calculation type from the "Calculate" dropdown. 4. Calculate. In "% change" mode, X is the old value and Y is the new value. A negative result means a decrease.

Formula Summary

**X% of Y = (X ÷ 100) × Y** **X as a % of Y = (X ÷ Y) × 100** **% change = ((Y − X) ÷ X) × 100**, where X is the old value and Y the new value | Mode | X | Y | Result | |---|---|---|---| | X% of Y | 20 | 150 | 30 | | X is what % of Y | 30 | 150 | 20% | | % change from X to Y | 250 | 300 | +20% | | % change from X to Y | 300 | 250 | −16.67% |

Worked Example

Sara's monthly salary rose from Rs 80,000 to Rs 92,000. % change = (92,000 − 80,000) ÷ 80,000 × 100 = 12,000 ÷ 80,000 × 100 = **15%** Her employer then deducts 10% for a provident fund contribution (illustrative figure): 10% of 92,000 = 0.10 × 92,000 = **Rs 9,200** Note the last row of the formula table: a rise from 250 to 300 is +20%, but a fall from 300 back to 250 is −16.67%, because the starting value changed.

Interpretation

A percentage is always relative to a base. "Up 20%" and "down 20%" do not cancel out: Rs 1,000 up 20% is Rs 1,200, and Rs 1,200 down 20% is Rs 960. Percentage points differ from percent. If a rate goes from 17% to 18%, it rose by 1 percentage point, which is a 5.88% increase in the rate itself. For adding or removing GST from a price, use the sales tax calculator, which handles tax-inclusive prices correctly.

Editorial Note

All formulas are standard arithmetic and the examples were checked by hand. The provident fund rate in the worked example is illustrative only. Last reviewed: October 2026.

Key Points

  • - X% of Y = X × Y ÷ 100.
  • - X as % of Y = X ÷ Y × 100.
  • - % change uses the old value as the base.
  • - Equal % rises and falls do not cancel out.
  • - Percentage points ≠ percent change.
  • - Removing a percentage from a tax-inclusive total needs division, not subtraction.

Common Uses

  • - Working out a discount during a sale.
  • - Calculating a salary increment percentage.
  • - Comparing bill or fuel price changes month to month.
  • - Finding what share of a budget goes to rent or school fees.
  • - Checking marks as a share of total (or use the marks percentage calculator).

Common Mistakes

  • - **Using the new value as the base.** Change is measured from the old value.
  • - **Subtracting a percentage to remove tax.** Rs 11,800 including 18% GST is Rs 10,000 before tax, not 11,800 − 18% = Rs 9,676.
  • - **Adding successive percentages.** Two 10% increases make 21%, not 20%.
  • - **Confusing points with percent.** 17% → 18% is +1 point, +5.88%.
  • - **Dividing by zero.** "% change" from 0 has no meaning; the calculator shows "—".

Search Topics

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  • - salary increment percentage
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  • - what percent is x of y
  • - discount percentage calculator pakistan

References

  • - No official source needed: standard arithmetic. The GST rate in the examples (18%) is from the Sales Tax Act, 1990, s.3(1): https://download1.fbr.gov.pk/Docs/202586148252375SalesTaxActupdatedupto2025-26.pdf

Faqs

How do I calculate 18% of a number?

Multiply the number by 18 and divide by 100. 18% of Rs 10,000 is Rs 1,800.

How do I find what percent one number is of another?

Divide the part by the whole and multiply by 100. 30 of 150 is 20%.

How do I calculate percentage increase in salary?

Subtract the old salary from the new one, divide by the old salary and multiply by 100. Rs 80,000 to Rs 92,000 is 15%.

Why is a 20% rise followed by a 20% fall not zero?

The fall is taken from the higher, new amount. Rs 1,000 → Rs 1,200 → Rs 960.

What is the difference between percent and percentage points?

Percentage points are the plain difference between two rates; percent change is that difference relative to the old rate.

Can I use this for marks percentage?

Yes, use "X is what % of Y". The marks percentage calculator does the same with clearer labels.

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