How to Calculate Percentage Decrease: Formula, Examples & Uses
Percentage decrease is one of the most frequently used calculations in everyday life — from figuring out how much you are saving in a sale, to tracking weight loss progress, to analyzing stock market dips. This guide explains the formula clearly and walks through practical examples so you always get it right.
For instant results, use our Percentage Decrease Calculator.
The Percentage Decrease Formula
Percentage Decrease = ((Original Value − New Value) ÷ Original Value) × 100
The key rule: always subtract the new (smaller) value from the old (larger) value. Then divide by the original value — not the new one.
Step-by-Step Worked Example
Problem: A laptop was priced at ₹75,000 and is now on sale for ₹60,000. What is the percentage decrease?
Step 1 — Find the difference: ₹75,000 − ₹60,000 = ₹15,000
Step 2 — Divide by the original value: ₹15,000 ÷ ₹75,000 = 0.20
Step 3 — Multiply by 100: 0.20 × 100 = 20%
The price has decreased by 20%.
How to Work Out Percentage Decrease: The Rules
- Always use the original value as the denominator. The decrease is measured relative to where you started.
- The result is always a positive number. Percentage decrease expresses magnitude, not direction — so even though the value fell, the percentage decrease is expressed as a positive figure (e.g., “a 20% decrease,” not “a −20% decrease”).
- If the result exceeds 100%, the value more than halved. A 100% decrease means the value reached zero.
Real-World Applications
1. Shopping Discounts and Sales
This is the most common use case. When a store advertises “30% off,” they are expressing a percentage decrease from the original price.
If a jacket costs ₹4,000 and drops to ₹2,800: (₹1,200 ÷ ₹4,000) × 100 = 30% decrease ✓
You can verify any advertised discount with this formula to make sure the math adds up.
2. Weight Loss Tracking
If someone weighed 90 kg and now weighs 81 kg: (9 kg ÷ 90 kg) × 100 = 10% decrease
Expressing weight loss as a percentage is more meaningful than raw kilograms because it accounts for starting body size.
3. Stock Market Drops
A share worth ₹500 falls to ₹380. (₹120 ÷ ₹500) × 100 = 24% decrease
Financial media always report market movements as percentage changes, because absolute numbers are meaningless without context. A ₹120 drop means something very different at ₹500 than it does at ₹5,000.
4. Cost Reduction in Business
A company’s raw material costs fall from ₹10 lakh to ₹8.5 lakh per month. (₹1,50,000 ÷ ₹10,00,000) × 100 = 15% cost reduction
Procurement and operations teams track cost reductions as percentages to benchmark efficiency improvements year over year.
5. Revenue Loss / Decline Analysis
Q2 revenue was ₹25 lakh; Q3 revenue fell to ₹20 lakh. (₹5 lakh ÷ ₹25 lakh) × 100 = 20% revenue decline
6. Fuel Economy Changes
Your car used to do 18 km/L and now does 15 km/L. (3 ÷ 18) × 100 = 16.7% decrease in fuel efficiency
Common Percentage Decrease Questions
“Decrease 61 by 24%”: 24% of 61 = 0.24 × 61 = 14.64 61 − 14.64 = 46.36
“Decrease 250 by 15%”: 15% of 250 = 0.15 × 250 = 37.5 250 − 37.5 = 212.5
“Reduce by 10%”: Multiply the original by 0.90
“Reduce by 50%”: Divide the original by 2
Percentage Decrease vs. Percentage Points
This distinction is frequently confused in media reporting:
- Percentage decrease: If a product’s market share drops from 40% to 32%, the percentage decrease is (8 ÷ 40) × 100 = 20% relative decrease.
- Percentage points: The market share fell by 8 percentage points.
These are two completely different measurements. Always check which one is being quoted.
Finding the Original Value (Working Backwards)
Sometimes you know the final price and the percentage decrease, but need to find the original price.
Formula: Original Value = Final Value ÷ (1 − Percentage Decrease ÷ 100)
Example: A discounted item costs ₹3,600 after a 10% reduction. What was the original price? Original = ₹3,600 ÷ (1 − 0.10) = ₹3,600 ÷ 0.90 = ₹4,000
Percentage Decrease vs. Percentage Increase: How They Relate
An important asymmetry: a 50% increase followed by a 50% decrease does not return you to the original value.
Start: ₹1,000 After 50% increase: ₹1,500 After 50% decrease from ₹1,500: ₹750
This asymmetry is critical in investing and price analysis. It is why a 50% portfolio loss requires a 100% gain just to break even.
Try the Calculator
For any specific numbers — especially complex decimals or reverse calculations — our Percentage Decrease Calculator gives instant, accurate results. You can also explore the Percentage Calculator for all-purpose percentage problems, or the Discount Calculator if you are specifically calculating sale prices.