To turn a percent into a decimal, divide the number by 100. This is the same as moving the decimal point two places to the left. So 25% becomes 0.25, 7% becomes 0.07, and 150% becomes 1.50. That single rule covers every case you’ll encounter.
The Basic Rule
The word “percent” literally means “per hundred.” When you see 45%, that means 45 out of 100, or 45 ÷ 100. Dividing by 100 gives you 0.45. Rather than doing long division every time, you can just move the decimal point two places to the left. Every whole number has an invisible decimal point at its right end, so 45 is really 45.0, and shifting that point two spots left gives you 0.45.
Here’s how it looks with a few common percentages:
- 50% → move the decimal two places left → 0.50
- 8% → 08.0 becomes 0.08
- 12.5% → 0.125
- 100% → 1.00
- 6% → 0.06
Small Percentages Under 1%
Percentages smaller than 1% trip people up because you need placeholder zeros. Take 0.5%, which you might see as a bank interest rate. Move the decimal two places left: 0.5 becomes 0.005. For 0.25%, the result is 0.0025. The rule doesn’t change; you just end up with more zeros after the decimal point. If you’re unsure, do the division longhand: 0.5 ÷ 100 = 0.005.
Percentages Over 100%
A percentage above 100 simply converts to a decimal greater than 1. Move the point two places left just like always. So 200% becomes 2.00, 350% becomes 3.50, and 112% becomes 1.12. You’ll see these in contexts like investment returns (“the stock rose 140%”) or growth rates.
Fractional Percentages
Sometimes a percent includes a fraction, like 6¾% or 33⅓%. Convert the fraction part to a decimal first, then apply the rule. 6¾% is the same as 6.75%, which becomes 0.0675. And 33⅓% equals roughly 33.333…%, which becomes 0.33333. Handle the fraction, then shift the decimal point.
Why This Conversion Matters
Calculators and formulas expect decimals, not percentages. Any time you need to multiply by a rate, whether for interest, discounts, taxes, or tips, you have to convert first. Here are a few real examples.
Calculating a discount. A store offers 15% off a $48 item. Convert 15% to 0.15, then multiply: $48 × 0.15 = $7.20 off. The sale price is $40.80.
Finding simple interest. You borrow $3,000 at 8% interest for one year. The interest formula is principal × rate × time. Convert 8% to 0.08, then calculate: $3,000 × 0.08 × 1 = $240 in interest.
Compound interest. If you invest $1,000 at 8% compounded annually for five years, the formula is future value = present value × (1 + rate)^n. Plug in the decimal: $1,000 × (1.08)^5 = $1,469.33. Writing 8 instead of 0.08 would give you a wildly wrong answer.
Depreciation. A $54,000 building depreciates at 20% this year. Convert to 0.20, multiply: $54,000 × 0.20 = $10,800 in depreciation.
Converting in Spreadsheets
In Excel or Google Sheets, a cell formatted as a percentage already stores the decimal internally. A cell showing 25% actually holds 0.25, so any formula referencing that cell uses the decimal automatically. You can confirm this by changing the cell format from Percentage to Number.
If you have a plain number like 25 in a cell and want to turn it into 0.25, just divide it by 100. In a new cell, type =A1/100 (replacing A1 with your cell reference). You can also type the percent sign directly into a cell: entering “25%” tells the spreadsheet to store 0.25.
Going the Other Direction
To convert a decimal back into a percent, reverse the process: multiply by 100, or move the decimal point two places to the right. So 0.75 becomes 75%, and 0.03 becomes 3%. Knowing both directions makes it easy to move between formats whenever a problem or formula calls for it.