Free · Everyday planning calculators
Add Up to Twenty Durations
Add up to twenty elapsed durations with compatible time units.
- Formula & worked example
- Private in your browser
- No signup
Calculator inputs
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How to use this calculator
- 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.
Private by default
Inputs and results stay in this browser tab. Bookify does not upload or store the values you enter.
Formula and method
Twenty one-hour sessions total twenty hours.
Total = sum of all twenty durations
Worked example
Enter these known values and leave the other values blank.
- Number of time entries
- 20
- Time 1
- 1 hrs
- Time 2
- 1 hrs
- Time 3
- 1 hrs
- Time 4
- 1 hrs
- Time 5
- 1 hrs
- Time 6
- 1 hrs
- Time 7
- 1 hrs
- Time 8
- 1 hrs
- Time 9
- 1 hrs
- Time 10
- 1 hrs
- Time 11
- 1 hrs
- Time 12
- 1 hrs
- Time 13
- 1 hrs
- Time 14
- 1 hrs
- Time 15
- 1 hrs
- Time 16
- 1 hrs
- Time 17
- 1 hrs
- Time 18
- 1 hrs
- Time 19
- 1 hrs
- Time 20
- 1 hrs
- Total time
- 20 hrs
Assumptions and limitations
- Every entered duration contributes to the total, including the ninth slot. Bookify corrects a captured formula that omitted that slot.
- This is elapsed-duration arithmetic; it does not apply clock dates, break deductions, payroll rules or overlapping-session logic.
Common questions
How should I interpret this result?
Every entered duration contributes to the total, including the ninth slot. Bookify corrects a captured formula that omitted that slot.
Can I solve a missing input?
Clear the value you want to find, enter compatible known values, and check the displayed units. Some choices and one-way outputs cannot be solved backward.
References
The twenty-slot form omits course_9 in the captured sum. Add all twenty terms and derive each inverse by subtracting the other nineteen terms. Independent one-hot and full-sum regressions prove every slot contributes once.
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