Backward Planning Calculator

Enter the deadline, estimate the work, and pick the available days. The calculator works backward from the deadline to a recommended start date, the latest safe start, and the number of work sessions you need.

Working days

How the calculator works

The calculator starts at the deadline and walks backward through the selected working days, reserving one work session at a time until the whole estimate is covered. The safety buffer moves the finish target earlier, so the recommended start leaves room for delays.

  1. Sessions needed: the total estimate divided by the session length, rounded up. The final session carries any remainder.
  2. Finish target: the deadline minus the safety buffer, snapped back to the nearest working day.
  3. Sessions are placed as late as possible, never more per day than the chosen maximum, and never before today.
  4. The recommended start is the first session's day. The latest safe start runs the same calculation without the buffer. Start later than that and the plan no longer fits.

A worked example

A report is due on Friday, September 18, 2026 at 17:00. The estimate is 4 hours of work in 2-hour sessions, at most one session per day, working Monday to Friday, with a 1-day safety buffer.

Change any input and the whole plan shifts. Adding a weekend day pulls the start later; doubling the estimate pushes it earlier; removing the buffer trades safety for slack.

Add the session plan to your calendar

Add to calendar downloads a standard calendar file (.ics). It contains one all-day event per work session and a separate deadline event. Each session event title includes the task name, its session number and total session count, and the planned duration. If you supply a deadline time, it appears in the deadline event.

Open or import it in Apple Calendar, Google Calendar, Outlook, or another compatible calendar. Choose the destination calendar, review the events, and confirm the import.

This is a one-time calendar export, so later calculator changes do not update imported events. The calculator creates the file in the browser, connects to no calendar account, and uploads nothing.

When and Deadline are two different dates

A Deadline is the last acceptable day to finish. A When is the day you plan to work on it. They may be the same date, but often are not. You set the Deadline, and the calculator finds the When. Pinwork uses the same two-date model, so you can add the result to a task without changing it. The distinction is covered in depth in Deadline vs. due date and the guide.

Frequently asked questions