Percentage Decrease Calculator

How it works

A percentage decrease tells you by how much a value has fallen, expressed as a proportion of the original. It is the mirror of percentage increase and follows a very similar formula.

The formula

Subtract the new value from the original, divide by the original, and multiply by 100. The result is always a positive number representing how much the value has fallen.

Why this works: The numerator (Old - New) gives the absolute size of the fall. Dividing by the original ensures the decrease is measured proportionally to where you started, not in absolute terms. A £500 fall means something very different on a £1,000 item than on a £100,000 house, and the percentage correctly captures that difference.

Related calculations

Use this calculator when tracking price drops, reduced costs, or any situation where a quantity has fallen. If you are unsure whether a value has gone up or down, you can track how a value has shifted in either direction. For shopping, you may want to find the sale price and exactly how much you save. If the item is marked as "percentage off", our percentage off tool shows the final price instantly.

Worked examples

When to use this

This calculation is particularly valuable in four common UK scenarios:

• Sale price reductions: A £950 sofa marked down to £760 in a Black Friday sale has dropped by 20%. Knowing the percentage helps you compare deals across different retailers rather than just looking at the pound saving.
• Energy cost savings: Switching energy supplier and cutting your annual bill from £1,800 to £1,440 is a 20% reduction. Expressed as a percentage, it is easier to compare with other household savings and budget changes.
• Property depreciation: A new car purchased for £22,000 that is worth £14,300 after three years has lost 35% of its value. Used-car valuation tools often quote depreciation as a percentage for exactly this reason.
• Business performance: A company whose monthly revenue falls from £85,000 to £72,250 has seen a 15% decline. Boards and managers use percentage decreases to benchmark performance consistently across teams and time periods.

Understanding the result

A percentage decrease of 50% means the value has halved. A decrease of 100% means it has reached zero. Values cannot decrease by more than 100% because you cannot have less than nothing (in most real-world contexts). If your result is unexpectedly large, check whether you have entered the original and new values in the correct order.

A small percentage decrease on a large number can still represent a significant absolute amount. A 2% drop in a £500,000 property value is a £10,000 fall. Always consider the context alongside the percentage figure.

Related concepts

➡ If you want to recover the starting price from a reduced figure, the reverse percentage calculator works backwards from a discounted amount to the original. ➡ To measure the arithmetic gap between two interest rates or tax rates, you can find the difference between two rates expressed in percentage points. ➡ To find the exact pound amount that any percentage represents, the percentage of a number tool gives the absolute figure directly.

How to do this in Excel

Put the original (higher) value in cell A1 and the new (lower) value in cell B1. The formula subtracts the new from the original, divides by the original, and multiplies by 100 to return the percentage decrease. If the result is negative, the "new" value is actually higher than the original, meaning the value has increased rather than decreased.

How to do this without a calculator

Subtract the new value from the original to find the fall in absolute terms. Then estimate the percentage by comparing that fall to the original. If a £120 bill drops to £96, the fall is £24. Dividing 24 by 120 gives 0.2, which is 20%. For quick mental arithmetic, find 10% of the original first by dividing by 10, then compare the actual fall to that 10% figure to estimate the percentage without a calculator.

Real world uses

• Working out how much a price has dropped during a Black Friday or January sale.
• Calculating the reduction in your monthly energy usage after switching to a cheaper tariff.
• Seeing the percentage fall in a used car's value since the original purchase date.
• Finding out how much a company's turnover has declined compared to the previous year.
• Measuring the drop in exam failure rates after a school introduces additional revision support.

Common mistakes

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