To write a number in expanded form, break apart a number, and write it as the sum of each place value. For example, 8324 = 8000 + 300 + 20 + 4. Decimals may also be expanded in a similar format: 0.239 = 0.2 + 0.03 + 0.009.

Expansion may be made simpler for teaching purposes or for beginners by setting up a chart or by first expressing the number using words.

The chart method uses a chart with the various place value names, and the number is written correctly into the chart. Multiply each digit by the appropriate power of 10 for the place value, before listing all values as a sum. For instance, 4827.65 expands as such:

Thousands: 4 x 1000 = 4000.

Hundreds: 8 x 100 = 800.

Tens: 2 x 10 = 20.

Units: 7 x 1 = 7.

Tenths: 6 x 1/10 = 0.6.

Hundredths: 5 x 1/100 = 0.05.

4000 + 800 + 20 + 7 + .6 + 0.05.

For the word method, write the number first using only words, and express each part individually. The sum is the expanded form of the number. For example, 4827.65 is written as "four thousand, eight hundred, twenty seven, six tenths, and five-hundredths," resulting in 4000 + 800 + 20 + 7 + 0.6 + 0.05.