Deck Board Calculator
Boards, screws, joists and cost for a deck of any size.
Enter your values
Enter the deck length in ft.
Enter the deck width in ft.
Enter the board width in in.
Enter the gap between boards in in.
Enter the board length sold in ft.
Enter the cost 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
- 26 (+10%: 29)
- Board rows
- 26
- Joists at 16 in o.c.
- 13 x 12 ft
- Screws (2 per joist crossing)
- 676
- Decking cost
- $638.00
- Deck area
- 192 sq ft
Working
- 126 rows x 1 board(s) per row = 26 boards
Quick answer
Board rows = deck width divided by board width plus gap; multiply by deck length and divide by board length to get pieces.
rows = deck width / (board width + gap)
At a glance
| What it does | Boards, screws, joists and cost for a deck of any size. |
|---|---|
| Category | Home & DIY |
| Inputs needed | Deck length, Deck width, Board width, Gap between boards, Board length sold, Cost per board |
| Main output | Deck boards |
| Formula | rows = deck width / (board width + gap) |
| Cost | Free — no sign-up, no download |
How to use the Deck Board Calculator
- 1Enter the deck footprint, then the actual board width (5.5 in for a nominal 6 in board).
- 2Set the expansion gap - 1/4 in for wood, check the maker's spec for composite.
- 3Add 10% for cuts, mitres and picture-frame borders.
Inputs explained
- Deck length(ft)
- Enter the deck length in ft.
- Deck width(ft)
- Enter the deck width in ft.
- Board width(in)
- Enter the board width in in.
- Gap between boards(in)
- Enter the gap between boards in in.
- Board length sold(ft)
- Enter the board length sold in ft.
- Cost per board($)
- Enter the cost per board in $.
Worked example
Using the values the calculator loads with:
Inputs
- Deck length16 ft
- Deck width12 ft
- Board width5.5 in
- Gap between boards0.25 in
- Board length sold16 ft
- Cost per board22 $
Results
- Deck boards26 (+10%: 29)
- Board rows26
- Joists at 16 in o.c.13 x 12 ft
- Screws (2 per joist crossing)676
- Decking cost$638.00
- Deck area192 sq ft
- 26 rows x 1 board(s) per row = 26 boards
Frequently asked questions
What gap should I leave between deck boards?
About 1/4 inch for dry hardwood or composite. Pressure-treated lumber that is still wet can be laid tight because it shrinks as it dries.
How many screws will I need?
Two per board per joist crossing. This tool counts them for you, and it is worth buying 10% extra.
What do I need to enter into the Deck Board Calculator?
Just 6 values: deck length, deck width, board width, gap between boards, board length sold, cost 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 Board Calculator work out the answer?
Board rows = deck width divided by board width plus gap; multiply by deck length and divide by board length to get pieces. It applies the formula rows = deck width / (board width + gap) and shows the working so you can check each step by hand.
Is the Deck Board 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.