To convert time to a decimal, use a conversion chart to look up the total minutes for the time to be converted. Note down the relevant value. For example, if the time to be converted is 4 hours and 10 minutes, retain the hours portion (4), and look up the value for 10 minutes. A conversion chart will show the corresponding value to be 0.17. The final decimal value is 4.17 hours.
Conversion charts are useful to express time in hours and minutes expressed as decimals. In other words, 3:45pm does not equal 3.45 hours; it converts to 3.75 hours. A conversion chart can show that 45 minutes converts to 0.75 hours (in other words, to three-fourths of an hour).
They are necessary because in telling time, minutes are expressed as a proportion of an hour (that is, as a proportion of 60), while many situations require time in the decimal format (that is, as a proportion of 100). For example, payroll calculations may require the total number of hours worked to be expressed as decimals.
Typically, conversion charts contain columns for minutes and the corresponding decimal figure. That is, the cell next to 19 minutes will show 0.32 hours, and 60 minutes will show 1.0 hour.
A simple way is to enter the number of hours, minutes and seconds into an online converter or calculator.
Several websites offer conversion charts and calculators, such as CalculateHours.com, EngineeringToolbox.com and CalculatorSoup.com.