Deck Cost & Materials Estimator

Deck Calculator

Calculate decking boards, fasteners, and total cost with flexible unit selection for accurate deck planning.

Length

Width

Total Area (m²)

Board Width

Board Length

Number of boards Fasteners used
Screws/Nails Hidden clips

Number of fasteners

Price per board (PKR) Price per fastener (PKR) Total Cost (PKR)

Deck Calculator — Decking Boards, Joists, Posts & Material Cost

A 12 x 16 ft deck (192 sq ft) requires approximately 420 linear feet of 2×6 decking, 13 joists, 3 beams, and 6 posts — using 16″ on-center joist spacing and 8 ft post spacing. Enter your deck dimensions in the calculator above to get a complete material list.

Add 10% waste for straight-lay decking. Add 15% for diagonal decking. Order concrete for footings at the same time — use the post hole concrete calculator at rainyroofers.com/post-hole-concrete-calculator to estimate footing volume.

How to Use the Deck Calculator

To get a deck material estimate, enter 4 values: deck length, deck width, decking board size, and joist spacing. The calculator returns board count, joist count, beam count, post count, fasteners, and total material cost.

Enter deck dimensions — length and width in feet; the calculator works in whole feet or decimals
Select decking board size — 5/4×6 is standard composite; 2×6 is standard pressure-treated
Choose joist spacing — 16″ on-center for most materials; 12″ for softer woods and thinner composites
Select decking material — PT lumber, cedar, redwood, or composite — pricing changes accordingly
Read your full material list — decking boards, joists, beams, posts, hardware, and total estimated cost

Deck Material Formula

Decking boards = Deck Area (sq ft) / Board Coverage per LF x Waste Factor — board coverage per linear foot depends on board width.

Worked Example — 12 x 20 ft Deck Using 2×6 Boards

Deck area = 240 sq ft. Board: 2×6 actual width = 5.5″ = 0.458 ft per LF.

LF of decking = 240 / 0.458 = 524 linear feet
With 10% waste: 524 x 1.10 = 576 linear feet to order
In 16-ft lengths: 576 / 16 = 36 boards of 2×6 x 16 ft

Complete Deck Components — What You Need to Order

Component	Material	Spacing / Spec	Purpose
Decking boards	2×6 PT or 5/4×6 composite	Perpendicular to joists	Walking surface
Joists	2×8 (spans to 12 ft)	16″ on center	Supports decking boards
Joists	2×10 (spans to 14 ft)	16″ on center	Longer spans
Rim joists	Same as joists	Perimeter only	Frame edge, attach railing
Beams	Doubled 2×10 or LVL	Max 8 ft apart	Carries joists to posts
Posts	6×6 PT	Max 8 ft apart	Transfers load to footings
Footings	Concrete (12″ diameter)	1 per post	Below frost line
Fasteners	Deck screws or hidden clips	2 per board per joist	Secures decking surface
Joist hangers	LUS26 (Simpson)	1 per joist each end	Connects joists to beams
Post bases	ABA66 (Simpson)	1 per post	Anchors post to footing

Deck Lumber by Size — Coverage and Board Count

Board Size	Actual Width	Coverage per LF	Boards per 100 sq ft
1×4	3.5″	0.292 ft/LF	34 boards x 12 ft
1×6	5.5″	0.458 ft/LF	22 boards x 12 ft
5/4×4 composite	3.5″	0.292 ft/LF	34 boards x 12 ft
5/4×6 composite	5.5″	0.458 ft/LF	22 boards x 12 ft
2×4	3.5″	0.292 ft/LF	34 boards x 12 ft
2×6	5.5″	0.458 ft/LF	22 boards x 12 ft

Deck Material Cost by Type

Decking Material	Material Cost/sq ft	Lifespan	Maintenance Required
Pressure-Treated Pine	.50-.00	15-25 years	Seal every 2-3 years; re-stain every 3-5 years
Cedar (Western Red)	.00-.00	20-30 years	Seal every 1-2 years to preserve color
Redwood	.00-.00	25-30 years	Seal every 2-3 years — naturally rot-resistant
Composite (standard)	.00-.00	25-30 years	Wash annually — no sealing or staining
Composite (premium PVC)	.00-5.00	30-50 years	Wash only — zero wood content
Tropical Hardwood (Ipe)	.00-5.00	40-75 years	Oil annually to maintain color; very dense

Joist and Beam Sizing — Span Table

Joist size depends on span between beams. Standard residential deck loads: 40 psf live load, 10 psf dead load, joists at 16″ on center:

Joist Size	Max Span (16″ OC)	Max Span (12″ OC)	Notes
2×6	9 ft 9 in	11 ft 2 in	Light-duty decks only — under 100 sq ft
2×8	12 ft 10 in	14 ft 9 in	Standard residential deck — most common choice
2×10	16 ft 5 in	18 ft 10 in	Large decks and elevated decks with long spans
2×12	19 ft 6 in	22 ft 5 in	Maximum span — very large or elevated structures

Beam sizing rule: double the joist material for beams. A deck using 2×8 joists uses doubled 2×8 beams bolted together with 1/2″ bolts at 12″ spacing. Use 6×6 PT posts for all elevated deck applications — 4×4 posts are only acceptable for ground-level decks under 30″ above grade.

Post Hole Concrete — How Much Do You Need?

Each deck post needs a concrete footing below the frost line. A 12-inch diameter footing at 42 inches deep uses 0.25 cubic feet of concrete per footing. For 6 posts: 6 x 0.25 = 1.5 cubic feet = 3 bags of 60-lb Sakrete.

Use the post hole concrete calculator at rainyroofers.com/post-hole-concrete-calculator to get exact bag count for any footing diameter and depth. Use the concrete weight calculator at rainyroofers.com/concrete-weight-calculator to verify footing load-bearing capacity.

Deck Fasteners — Screws, Clips, and Hardware

Fastener Type	Count Formula	Cost Estimate	Best Use
Deck screws (3″ #10)	2 per board per joist	5-0 per lb (200 screws)	Standard PT lumber, cedar decking
Hidden clips (composite)	1 clip per board per joist	/bin/sh.30-/bin/sh.60 per clip	Composite and PVC decking
Joist hanger screws (1.5″)	10 per hanger	-2 per lb	Structural — do not substitute with standard screws
Post base anchors	1 per post	-8 each	Anchors 6×6 post to concrete footing
Through-bolts (1/2″ x 5″)	2 per beam splice	– each	Joins doubled beam members

Deck Calculator by Project Size

Small Deck — 10 x 12 ft (120 sq ft)

Requires 263 LF of 2×6 decking (16 boards x 16 ft), 9 joists (2×8), 2 beams, 4 posts, and 4 concrete footings. Material cost: 00-,200 for PT lumber; ,500-,400 for composite.

Medium Deck — 12 x 16 ft (192 sq ft)

Requires 420 LF of 2×6 decking (27 boards x 16 ft), 13 joists (2×8), 3 beams, 6 posts, and 6 footings. Material cost: ,000-,000 for PT lumber; ,500-,000 for composite.

Large Deck — 16 x 20 ft (320 sq ft)

Requires 700 LF of 2×6 decking (44 boards x 16 ft), 16 joists (2×10), 4 beams, 8 posts, and 8 footings. Material cost: ,800-,200 for PT lumber; ,000-,000 for composite.

Frequently Asked Questions

How much lumber do I need for a 12x16 deck?

27 boards of 2×6 x 16 ft for decking, plus 13 joists, 3 beams, and 6 posts for a standard 192 sq ft deck. Use the lumber calculator at rainyroofers.com/lumber-calculator to price individual components.

What is the best joist spacing for a deck?

16 inches on center is the standard spacing for most residential deck materials — PT lumber, cedar, and standard composite decking. Use 12″ spacing for thinner composite boards under 1″ or for diagonal decking layouts.

How deep do deck footings need to be?

Footings must extend below the frost line — 36-48 inches in cold climates, 12-18 inches in warm climates. Check your local building code for the required frost depth. Footings above the frost line heave in winter and crack concrete over time.

Should I use pressure-treated or composite decking?

Use pressure-treated lumber for budget builds; use composite for low-maintenance longevity. PT lumber costs .50-.00/sq ft and lasts 15-25 years with regular sealing. Composite costs .00-5.00/sq ft and lasts 25-50 years with no sealing.

How many screws do I need for a deck?

Use 2 screws per board per joist crossing. A 12×16 ft deck with 13 joists and 27 boards requires: 27 x 13 x 2 = 702 screws. Buy 1 lb (approx. 200 screws) per 100 sq ft of deck as a starting estimate.

Do I need a permit to build a deck?

Yes for most decks over 30 inches above grade or attached to the house. Ground-level freestanding decks under 200 sq ft are exempt in most jurisdictions. Always check local building codes before starting. Attached decks require a ledger connection inspection in all US states.