Deadline Calculator
Work out the latest date you can start a task and still finish on time.
Formula and sources updated · Data sources · 1View algorithm, constants and default inputs (JSON)
Results
About this calculator
Estimate the latest project start date from work hours, buffers, revisions and review time. “Weekdays only” skips Saturdays and Sundays while counting both the task and review days; it does not account for public holidays.
Worked example
calculated with the default values below
Deadline 2027-01-31 · Estimated work hours 20 h · Hours you can work per day 3 h · Buffer 20 % · Revision rounds 1 · Days needed for review 2 days · Working days only Weekdays only Total hours including buffer and revisions 27.6 h · Working days needed 10.0 days · Latest start date 2027-01-14 · Calendar days from now 75 days · Feasible? Yes — you have 75 days before the latest start · Note Weekends are skipped when counting work and review days
Method and assumptions
H = E(1 + b ÷ 100)(1 + 0.15R); d_w = ⌈H ÷ h⌉; L = due − (d_w + v)d Required days are rounded up after buffer and revision adjustments. Weekday-only mode counts backward while skipping Saturdays and Sundays for work and review; holidays are not modeled. Estimate the latest project start date from work hours, buffers, revisions and review time. “Weekdays only” skips Saturdays and Sundays while counting both the task and review days; it does not account for public holidays. The references provide context and limitations. They do not validate this page’s illustrative multipliers, lookup values or predictions.
Data sources
The references provide context and limitations. They do not validate this page’s illustrative multipliers, lookup values or predictions.
Disclaimer
These calculators give general date results. Public holidays, working-day conventions and time-zone rules are set locally and change, so confirm against the official calendar for anything legally or contractually binding.
Implementation source
This record describes the implementation used by this page. It is not independent validation. External references, when available, support only the stated formula or definition; estimates and custom rules retain their own assumptions.
Formula and variables
H = E(1 + b ÷ 100)(1 + 0.15R); d_w = ⌈H ÷ h⌉; L = due − (d_w + v)d
- E
- Estimated hours
- b
- Buffer percent
- R
- Revision rounds
- H
- Total hours
- h
- Hours per workday
- d_w
- Working days needed
- v
- Review days
- d
- One day in milliseconds (86400000)
- due
- Due date
- L
- Latest start date
Required days are rounded up after buffer and revision adjustments. Weekday-only mode counts backward while skipping Saturdays and Sundays for work and review; holidays are not modeled.
Frequently asked questions
How does weekday-only scheduling work?
The estimate adds buffer and 15% per revision round, rounds required workdays up, then counts backward from the due date. In weekday-only mode, both work and review days skip Saturday and Sunday. Holidays are not included, and the result is a planning estimate rather than a guarantee.
Which inputs and limits apply to Deadline Calculator?
Use the units shown beside each field. These are form limits, not recommended settings. Estimated work hours: 0.5–5,000 h; Hours you can work per day: 0.5–24 h; Buffer: 0–100 %; Revision rounds: 0–10; Days needed for review: 0–60 days H = E(1 + b ÷ 100)(1 + 0.15R); d_w = ⌈H ÷ h⌉; L = due − (d_w + v)d Required days are rounded up after buffer and revision adjustments. Weekday-only mode counts backward while skipping Saturdays and Sundays for work and review; holidays are not modeled. Estimate the latest project start date from work hours, buffers, revisions and review time. “Weekdays only” skips Saturdays and Sundays while counting both the task and review days; it does not account for public holidays. The references provide context and limitations. They do not validate this page’s illustrative multipliers, lookup values or predictions.
What is a complete worked example for Deadline = 2027-01-12; Estimated work hours = 20 h?
Inputs: Deadline = 2027-01-12; Estimated work hours = 20 h; Hours you can work per day = 3 h; Buffer = 20 %; Revision rounds = 1; Days needed for review = 2 days; Working days only = Weekdays only. Calculation: H = E(1 + b ÷ 100)(1 + 0.15R); d_w = ⌈H ÷ h⌉; L = due − (d_w + v)d. Results: Total hours including buffer and revisions = 27.6 h; Working days needed = 10.0 days; Latest start date = 2026-12-25; Calendar days from now = 74 days; Feasible? = Yes — you have 74 days before the latest start; Note = Weekends are skipped when counting work and review days. Reference date: 2026-10-12 (UTC).