SSC and bank exam aspirants in Delhi's Mukherjee Nagar practise percentages until they can do them faster than a calculator, because the clock decides the result. Shopkeepers in any bazaar do the same with discounts. These percentage shortcuts are the ones that come up again and again, each with a worked example.
1. Build from 10% and 1%
10% is the number with the decimal moved one place; 1% moves it two places. Everything else is built from those. 17% of 640 = 10% (64) + 5% (32) + 2% (12.8) = 108.8.
2. Swap the numbers
x% of y equals y% of x. 8% of 50 is hard to picture, but 50% of 8 is obviously 4.
Try the free Percentage Calculator
Instant result in your browser. No sign-up, nothing stored.
3. Know the fraction table
| Percentage | Fraction | Percentage | Fraction |
|---|---|---|---|
| 50% | 1/2 | 12.5% | 1/8 |
| 33⅓% | 1/3 | 11.11% | 1/9 |
| 25% | 1/4 | 9.09% | 1/11 |
| 20% | 1/5 | 8.33% | 1/12 |
| 16⅔% | 1/6 | 6.25% | 1/16 |
| 14.28% | 1/7 | 5% | 1/20 |
37.5% of 480 = 3/8 × 480 = 180.
4. Percentage change: always divide by the old value
Price ₹250 → ₹300 is (50 ÷ 250) = +20%. Back from ₹300 → ₹250 is (50 ÷ 300) = −16.67%. The base changes, so the percentages differ.
5. Successive changes multiply
Net change = a + b + (a × b ÷ 100) (use negatives for decreases)
A 20% rise followed by a 20% fall: 20 − 20 − 4 = −4%. Two discounts of 20% and 10%: −20 − 10 + 2 = −28%, not −30%.
6. Remove GST from an inclusive price
Divide by (1 + rate): ₹1,180 including 18% GST is 1,180 ÷ 1.18 = ₹1,000. Taking 18% off ₹1,180 (giving ₹967.60) is a classic mistake.
7. Marks to percentage out of 500 or 600
Out of 500, divide by 5: 436/500 = 87.2%. Out of 600, divide by 6: 512/600 = 85.33%.
8. Reverse: what number is X% of?
If 15% is 45, then 1% is 3 and 100% is 300.
9. Profit and loss in one line
Bought at ₹800, sold at ₹920: profit 120 ÷ 800 = 15%. Profit percentage is on the cost price unless a question says otherwise.
10. Quick sanity check
Round both numbers and estimate first. 23% of 4,870 should be a bit under a quarter of 5,000, so around 1,100–1,150. The exact answer, 1,120.1, fits.
Which trick saves the most time in exams?
The fraction table. Once 1/8 = 12.5% and 1/12 = 8.33% are automatic, most percentage questions in SSC and bank papers become one-step fractions.
Using percentage shortcuts under exam pressure
Practise each trick until it's automatic, then mix them in timed sets of 20 questions. In SSC and bank papers, most percentage questions combine two ideas (a successive change plus a reverse percentage, or a fraction plus a profit calculation), so speed comes from recognising which shortcut fits in the first few seconds. Write the fraction table on a card and revise it daily for two weeks.
For exact answers, the percentage calculator handles percentage of a number, X as a percent of Y, change, marks, discounts and reverse (GST-inclusive) percentages.
Frequently asked questions
What is the fastest way to calculate a percentage?
Build it from 10% and 1%, or use a fraction equivalent like 12.5% = 1/8.
How do I calculate two successive percentage changes?
Net change = a + b + ab/100. A 20% rise then a 20% fall is −4%.
How do I remove GST from a price?
Divide by (1 + GST rate). ₹1,180 including 18% GST is ₹1,000 before GST.
How do I convert marks out of 500 into percentage?
Divide the marks by 5. 436/500 is 87.2%.
Is x% of y the same as y% of x?
Yes. For example, 8% of 50 = 50% of 8 = 4.
Keep reading
- Percentage Calculator: the free tool this guide explains.
- All math & utility calculators
- IRCTC 60 Day Booking Rule: Plan Festival Trains Without Stress
Sources: standard percentage arithmetic.