Quick answer
Each block starts when the previous one ends plus a buffer. Tasks of 90, 45, 30 and 60 minutes starting at 09:00 with 10-minute buffers run 09:00–10:30, 10:40–11:25, 11:35–12:05 and 12:15–13:15.
Enter task durations, a start hour and a buffer. The calculator returns each block and the finish time. Use this time blocking calculator to check your own figures.
Related tools: Time Allocation Calculator: Split a block of time between activities by percentage. Time Saved Calculator: Hours saved over a year by speeding up a task. Focus Session (Pomodoro) Calculator: How many focus sessions and breaks fit in the time you have.
How to use the Time Blocking Calculator
- Type task durations in minutes, separated by commas, for example 90, 45, 30, 60.
- Enter start time (hour, 0 to 23.99; 9.5 = 9:30) (between 0 and 23.99). It starts at 9.
- Enter buffer between blocks (minutes) (between 0 and 120). It starts at 10.
- Press Calculate to see the result, and use Reset to start again.
| Input | What to enter | Allowed values |
|---|---|---|
| Task durations in minutes, separated by commas | Text, such as 90, 45, 30, 60 | — |
| Start time (hour, 0 to 23.99; 9.5 = 9:30) | A number | ≥ 0, ≤ 23.99, starts at 9 |
| Buffer between blocks (minutes) | A number | ≥ 0, ≤ 120, starts at 10 |
Formula and method
Formula
block k starts when block k−1 ends plus the buffer
IEEE-754 double precision; shown to at most 6 decimal places.
Places the tasks in the order given, one after the other, starting at the chosen time, with the buffer between blocks (no buffer after the last). It reports each block's start and end clock time and the total time. Up to 20 tasks.
Worked examples
These examples are verified: each one is an automated test case that the live calculator must reproduce exactly.
Example 1
Inputs: Task durations in minutes, separated by commas = 90, 45, 30, 60; Start time (hour, 0 to 23.99; 9.5 = 9:30) = 9; Buffer between blocks (minutes) = 10.
| Result | Value |
|---|---|
| Finish time | 13:15 |
| Block 1 (90 min) | 09:00 – 10:30 |
| Block 2 (45 min) | 10:40 – 11:25 |
| Block 3 (30 min) | 11:35 – 12:05 |
| Block 4 (60 min) | 12:15 – 13:15 |
| Total time including buffers | 255 min |
Example 2
Inputs: Task durations in minutes, separated by commas = 30; Start time (hour, 0 to 23.99; 9.5 = 9:30) = 14.5; Buffer between blocks (minutes) = 15.
| Result | Value |
|---|---|
| Finish time | 15:00 |
| Block 1 (30 min) | 14:30 – 15:00 |
| Total time including buffers | 30 min |
Example 3
Inputs: Task durations in minutes, separated by commas = 60, 60; Start time (hour, 0 to 23.99; 9.5 = 9:30) = 22; Buffer between blocks (minutes) = 0.
| Result | Value |
|---|---|
| Finish time | 00:00 |
| Block 1 (60 min) | 22:00 – 23:00 |
| Block 2 (60 min) | 23:00 – 00:00 |
| Total time including buffers | 120 min |
The first line is the headline result (finish time). Below it the time Blocking Calculator lists block 1 (90 min), block 2 (45 min), block 3 (30 min), block 4 (60 min) and total time including buffers, which describe the same case from other angles. IEEE-754 double precision; shown to at most 6 decimal places.
Why buffers
Buffers absorb overruns and transitions. Three buffers here add 30 minutes to a 225-minute plan.
Where this estimate stops applying
Times past midnight wrap around the clock, and up to 20 tasks are supported.
How the result changes with start time
Holding every other input at the first worked example, this table changes only start time. It shows how sensitive the answer is to that one value; each row was produced by running this calculator.
| Start time | Finish time | Block 1 (90 min) | Block 2 (45 min) |
|---|---|---|---|
| 4.5 | 08:45 | 04:30 – 06:00 | 06:10 – 06:55 |
| 9 | 13:15 | 09:00 – 10:30 | 10:40 – 11:25 |
| 18 | 22:15 | 18:00 – 19:30 | 19:40 – 20:25 |
What happens with invalid input
These messages are produced by the calculator itself, so you know what to fix.
- Task durations in minutes, separated by commas: left empty shows "Enter task durations in minutes, separated by commas." beside that field and no result.
Choosing between the Time Blocking Calculator and similar calculators
Each row shows what a related calculator on this site asks for and what it returns, so you can pick the one that matches your question.
| Calculator | You enter | It returns |
|---|---|---|
| [Time Allocation Calculator](/time/time-allocation-calculator/) | total time, activity 1 and activity 2 | Activity 1 |
| [Time Saved Calculator](/lifestyle/time-saved-calculator/) | times the task is done per day, minutes saved each time and working days per year | Time saved per year |
| [Focus Session (Pomodoro) Calculator](/time/focus-time-calculator/) | time available, focus session and short break | Focus sessions |
| [Hourly Productivity Calculator](/time/hourly-productivity-calculator/) | units completed and hours worked | Units per hour |
| [Pomodoro Sessions Calculator](/time/pomodoro-sessions-calculator/) | time available, focus session and short break | Focus sessions |
Background: dates and times
Date and time results depend on the conventions a tool uses: whether the end date counts, whether weekends and holidays are skipped, how months of different lengths are handled and whether time zones are applied. This page states its convention, and the worked examples show it.
Dates use the Gregorian calendar and calendar days unless the page says otherwise; check deadlines against the rule in your contract or regulation.
Assumptions and limitations
- Times past midnight wrap around the clock
- Maximum 20 tasks
If a required value is empty, not a number, or outside its allowed range, the form marks that field with a message and shows no result instead of a misleading number. The automated checks deliberately try invalid entries for task durations in minutes, separated by commas to confirm this.
Frequently asked questions
What buffer is typical?
A buffer of 5 to 15 minutes between blocks is typical to absorb overruns and transitions.
Can I include lunch?
Yes, add lunch as a task with its duration, e.g. 45 minutes, and it is scheduled between the other blocks.
Does it reorder tasks?
No. Tasks are scheduled in the order you list them; reorder the list to change the sequence.
What does the Time Blocking Calculator calculate?
Lay tasks back to back from a start time, with a buffer between blocks. It returns Finish time, Block 1 (90 min), Block 2 (45 min), Block 3 (30 min) and Block 4 (60 min).
What formula does the Time Blocking Calculator use?
block k starts when block k−1 ends plus the buffer. Places the tasks in the order given, one after the other, starting at the chosen time, with the buffer between blocks (no buffer after the last).
What do I need to enter in the time Blocking Calculator?
You enter Task durations in minutes, separated by commas, Start time (hour, 0 to 23.99; 9.5 = 9:30) and Buffer between blocks (minutes).
How is the result rounded or limited?
IEEE-754 double precision; shown to at most 6 decimal places. Times past midnight wrap around the clock.
What are the limits of this calculator?
Times past midnight wrap around the clock. Maximum 20 tasks.
What is an example of a time Blocking result?
With task durations in minutes, separated by commas 90, 45, 30, 60, start time (hour, 0 to 23.99; 9.5 = 9:30) 9 and buffer between blocks (minutes) 10, the finish time is 13:15.
Where does the method come from?
The method follows: Sequential scheduling arithmetic.
Related calculators
- Time Allocation Calculator — Split a block of time between activities by percentage.
- Time Saved Calculator — Hours saved over a year by speeding up a task.
- Focus Session (Pomodoro) Calculator — How many focus sessions and breaks fit in the time you have.
- Hourly Productivity Calculator — Output per hour, time per unit and the hours needed to reach a target.
- Pomodoro Sessions Calculator — Number of focus sessions that fit in the time you have.
- Project Duration Calculator — Working days and finish date for a project from total effort, team size and daily hours.
Sources
- Sequential scheduling arithmetic
Content last reviewed 2026-11-04. Formulas and worked examples are checked by automated tests against independently computed values.