Project Timeline Calculator
Work out how long a project will take — up to four tasks with durations and dependencies, with start and finish days for each.
A project is not one duration — it is tasks that wait for each other. This calculator follows the chain: each task starts when its dependency finishes, and the longest chain sets the total.
Durations are yours to enter. This is a planning estimate, not a schedule guarantee.
Your results
Enter your measurements and press Calculate.
Quantities are rounded up to whole tiles, planks, boxes or bags, after the wastage allowance. Cost appears only when you enter a price.
Formula
All lengths are converted to a single unit before the calculation: 1 ft = 0.3048 m, 1 in = 25.4 mm, 1 ft² = 0.09290304 m², 1 yd² = 9 ft². Material quantities are rounded up — you cannot buy part of a tile, plank or bag.
How to use this calculator
- Enter each task's duration in days.
- Choose what each task depends on (or nothing).
- Leave task 4 blank if the project has only three tasks.
- Read each task's start and finish day, and the total duration.
Worked example
| Tasks | Demolition 3 days → Framing 5 days → Drywall 4 days → Painting 3 days, each depending on the last |
|---|---|
| Demolition | Days 0–3 |
| Framing | Days 3–8 |
| Drywall | Days 8–12 |
| Painting | Days 12–15 |
| Total | 15 days (the critical path) |
Check it by hand: every step above uses the formula in the box. If your numbers match the example inputs but the calculator gives a different answer, please report it via the contact page.
Frequently asked questions
What is a critical path?
The longest chain of dependent tasks — it sets the project duration. If demolition, framing, drywall and painting each depend on the last, the total is their sum (15 days). Tasks with no dependency run in parallel and do not add to the total.
Can a task depend on a later task?
No — a task can only depend on an earlier task, or on nothing. A later dependency would be a circle: the task would wait for itself. The calculator rejects it.
How do I estimate task durations?
From experience or contractor quotes — enter your own figures. Add buffer for drying times (plaster, paint, concrete) and for inspections, which are not tasks here.
Is this a guaranteed schedule?
No. It is a planning estimate from your own durations. Real projects slip — deliveries, weather, inspections and hidden work all add days. Keep a buffer in the plan.
Related calculators
Estimates only. Results are for planning. Measure twice, confirm box coverage and tile sizes on the packaging you buy, and follow the manufacturer's instructions. See the disclaimer.