Deck Calculator
Boards, joists and cost for a deck.
Enter your values
Enter the deck length in ft.
Enter the deck width in ft.
Enter the board width in inches.
Enter the gap between boards in inches.
Enter the price per board in $.
Results update instantly as you type — no submit needed. Your values are remembered on this device, and the shareable link reopens the calculator with exactly these numbers.
- Deck boards (16 ft)
- 28
- Board rows
- 26
- Joists at 16 in centres
- 13
- Deck area
- 192 sq ft
- Estimated board cost
- $504.00
Quick answer
Deck board count depends on deck area, board width and the gap between boards, plus joists at 16 inch centres.
At a glance
| What it does | Boards, joists and cost for a deck. |
|---|---|
| Category | Home & DIY |
| Inputs needed | Deck length, Deck width, Board width, Gap between boards, Price per board |
| Main output | Deck boards (16 ft) |
| Cost | Free — no sign-up, no download |
How to use the Deck Calculator
- 1Enter your deck dimensions.
- 2Enter board width and spacing gap.
- 3Add 5% for cuts and defects.
Inputs explained
- Deck length(ft)
- Enter the deck length in ft.
- Deck width(ft)
- Enter the deck width in ft.
- Board width(inches)
- Enter the board width in inches.
- Gap between boards(inches)
- Enter the gap between boards in inches.
- Price per board($)
- Enter the price per board in $.
Worked example
Using the values the calculator loads with:
Inputs
- Deck length16 ft
- Deck width12 ft
- Board width5.5 inches
- Gap between boards0.25 inches
- Price per board18 $
Results
- Deck boards (16 ft)28
- Board rows26
- Joists at 16 in centres13
- Deck area192 sq ft
- Estimated board cost$504.00
Frequently asked questions
What gap should I leave?
1/8 to 1/4 inch for pressure-treated boards that will shrink as they dry.
How deep are footings?
Below your local frost line — often 36–48 inches in cold climates.
What do I need to enter into the Deck Calculator?
Just 5 values: deck length, deck width, board width, gap between boards, price per board. Every field starts with a realistic example, so you can change one number at a time and watch the result update instantly.
How does the Deck Calculator work out the answer?
Deck board count depends on deck area, board width and the gap between boards, plus joists at 16 inch centres. The working is shown step by step so you can verify the result by hand.
Is the Deck Calculator free, and do I need an account?
It is completely free with no sign-up, no download and no usage limit. Everything is calculated in your browser, so the numbers you type never leave your device.
Results are estimates for general information. For medical, legal, structural or financial decisions, confirm with a qualified professional.