Free · Everyday calculations

Twenty-Entry Duration Sum & Missing Time

Add up to twenty signed durations in hours, minutes and seconds, or solve a missing duration from the total.

Calculator inputs

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Enter the known values in the units shown. Results update as you type.
Where results are editable, change one to solve backwards. Lock a value to hold it fixed.
Use the worked example to check the method. Reset restores the starting fields.

Inputs and results stay in this browser tab. Bookify does not upload or store the values you enter.

One hour 30 minutes, two hours 15 minutes and 45 minutes total four hours 30 minutes, including when the third value is entered in slot nine.

Total duration = sum of entries 1 through 20; missing duration = total − sum of the other entries

Enter these known values and leave the other values blank.

These are elapsed durations, not clock times or calendar dates. Time zones, daylight-saving transitions, overnight schedules and unpaid breaks are not inferred.
Enter hours:minutes:seconds for the default compound controls. A leading minus sign negates the entire duration; signed adjustments are supported.
The first two entries start blank; unused later entries start at zero. Reducing the entry count does not erase a nonzero later entry: it remains visible and included.
The total preserves the source inverse calculations and includes all twenty slots. Bookify corrects the captured formula that omitted slot nine.

Yes. Change an entry unit to hours; 1.5 then means one hour 30 minutes. In a compound control, use 1:30:00 instead.

Yes. Leave it blank, enter the other durations and supply the total. The calculator subtracts the known durations from the total.

Bookify includes the omitted ninth duration in the total and every retained inverse, and adds the corresponding missing-ninth-duration inverse.