Deck Calculator
Calculate lumber, joists, posts, concrete footings, and hardware needed for your deck project with cost estimates.
Deck Shape
Deck Dimensions
ft
ft
Decking Options
Stairs (Optional)
Include Stairs
ft
Railing (Optional)
Include Railing
ft
Typically 3 sides of deck perimeter (one side attached to house)
Cost Estimate (Optional)
$
Materials only. $15-30 PT lumber, $25-40 cedar, $30-60 composite
Deck Materials Needed
192
Total Sq Ft
42
Deck Boards
Joists
0
2x8 or 2x10
Posts
0
4x4 or 6x6
Concrete
0
bags (80 lb)
Screws
0
lbs
Complete Materials List
Framing
Ledger Board (2x8 or 2x10)
1 x 16 ft
Rim Joists (2x8 or 2x10)
3 boards
Floor Joists (2x8 or 2x10)
10 boards
Beams (2x8 or 2x10 doubled)
4 boards
Decking
Deck Boards (5/4x6 or 2x6)
42 boards
Support
Posts (4x4 or 6x6)
6 posts
Concrete for Footings (80 lb bags)
12 bags
Hardware
Deck Screws (3" exterior)
5 lbs
Joist Hangers
20 pcs
Post Brackets
6 pcs
Ledger Board Bolts (1/2" x 6")
8 bolts
Deck Layout Diagram
Posts
Beams
Joists
Decking
Deck Building Tips
Foundation & Footings
- Dig footings below the frost line (36-48" in most areas)
- Use 12" diameter concrete tube forms for footings
- Set post brackets in wet concrete for proper alignment
- Allow concrete to cure 24-48 hours before building
- Check local building codes for footing requirements
Framing Best Practices
- Use pressure-treated lumber for all framing
- Crown joists upward when installing
- Use joist hangers instead of toe-nailing
- Double up beams for spans over 8 feet
- Install blocking between joists for rigidity
Decking Installation
- Leave 1/8" gap between boards for drainage
- Pre-drill near board ends to prevent splitting
- Use 2 screws per joist crossing
- Stagger board joints for a cleaner look
- Let boards acclimate to outdoor conditions 2-3 days
Frequently Asked Questions
How do I calculate how many deck boards I need?
Divide your deck's square footage by the coverage area of one board (board length times board width in feet). For standard 5.5-inch wide boards on a 12-foot run, each board covers about 5.5 square feet. Add 10-15% extra for waste, cuts, and mistakes. Our calculator handles this automatically.
What is the proper joist spacing for a deck?
Standard joist spacing is 16 inches on center for most residential decks using standard decking. Use 12-inch spacing for diagonal decking patterns or composite materials that require more support. 24-inch spacing may be acceptable for heavy-duty lumber but check local codes and manufacturer recommendations.
How many posts and footings do I need for a deck?
Posts are typically spaced 6-8 feet apart along beam lines. For a basic rectangular deck, you need posts at each corner plus intermediate posts. Each post requires a concrete footing - typically 12-inch diameter holes filled with concrete, extending below the frost line (usually 36-48 inches deep depending on your region).
How much does it cost to build a deck per square foot?
Material costs typically range from $15-30 per square foot for pressure-treated lumber, $25-40 for cedar or redwood, and $30-60 for composite decking. Labor adds another $15-35 per square foot. Total costs including materials and labor typically range from $30-75 per square foot for most residential decks.