1. Open your spreadsheet and locate the duration column
In Google Sheets, open your file and find the column (e.g., Column B) that contains durations in hh:mm:ss
format.
2. Format the duration column as Duration
Select the entire column with durations, then go to the Format
menu → Number
→ Duration
so that Google Sheets treats the values as time.
3. Insert a new column labeled Seconds
Add a column next to the duration column. In the header cell, enter Seconds to label it for the converted values.
4. Enter the formula to convert duration to seconds
In a cell in your Seconds column, type the formula: =B2*86400
. This multiplies the duration by the number of seconds in a day (86400), since durations in Google Sheets are stored as fractions of 24 hours.
5. Format the Seconds column as NumberHighlight the new column, go to the Format
menu → Number
→ Number
so that values appear as whole numbers instead of time.
6. Copy the formula down to the remaining rows
Drag the fill handle down the column to apply the formula to all rows with a duration value.