How the deck cost calculator prices a deck
Deck contractors usually price the platform by the square foot and the railing by the linear foot, because a railing costs the same per foot whether the deck is large or small. Stairs are priced per set. Entering the three separately lets you compare two bids that split the work differently, and lets you see what a smaller deck or a lower deck without railing would save.
| Deck | Area | Railing (3 sides) | Perimeter |
|---|---|---|---|
| 10 × 10 ft | 100 sq ft | 30 ft | 40 ft |
| 12 × 12 ft | 144 sq ft | 36 ft | 48 ft |
| 12 × 16 ft | 192 sq ft | 44 ft | 56 ft |
| 14 × 16 ft | 224 sq ft | 46 ft | 60 ft |
| 16 × 20 ft | 320 sq ft | 56 ft | 72 ft |
| 20 × 20 ft | 400 sq ft | 60 ft | 80 ft |
The railing column assumes the long side runs along the house and the other three sides are open; subtract the width of the stair opening, which gets stair rails instead. A freestanding deck needs railing on all four sides if it is high enough to need any.
What a deck costs: the survey number
Homeowners reported 3.86 million porch, deck, patio and terrace jobs in the Census Bureau's 2023 American Housing Survey, with a median cost of $4,750 and an average of $8,860.[1] The category mixes new decks with repairs and patios, and it includes do-it-yourself work, so a contractor-built deck can land well above the median. Use it as a sanity check on your total, not as a price.
When a deck needs a guard (railing)
A deck needs a guard where its walking surface is more than 30 inches above the ground at any point within 36 inches horizontally of the open edge. That is the 2021 International Residential Code rule as summarized by Washington building departments, which also note guards must be designed for a 200-pound load along the top.[2] Because the test uses the ground near the edge, a deck on a slope can need a guard on one side and not on another. A deck built under that height can skip railing, which the calculator reflects when you set railing to zero; check your own jurisdiction, since some require more.
Call 811 before footingsDeck footings are digging. Every state has a one-call center and requires a call 48 to 72 hours before you dig, for homeowners as well as contractors, so that buried lines are marked.
That requirement comes from the federal pipeline safety agency's guidance on state one-call laws.[3]
Worked example: a 16 × 12 ft deck
- Area: 16 × 12 = 192 sq ft × your installed price per square foot.
- Railing: 12 + 16 + 12 = 40 ft on the open sides, 36 ft after a 4 ft stair opening, × your price per foot.
- Stairs: 1 set × your price per set.
- Permit and other items: from the building department and the quote.
The calculator also returns the all-in price per square foot, which is the fair way to compare a bid that includes railing with one that does not.
Paying for a deck
A new deck adds to a home's value, which the IRS treats as an improvement rather than a repair; interest on home equity debt used for it can be deductible if you itemize and stay within the limits.[4] For a one-time job with a fixed price, a home equity loan's single payout and usually fixed rate fits well; a HELOC lets you draw only what you use, usually at a variable rate.[5] Both are secured by the house.[6] Run the numbers in the home improvement loan calculator, and see the fence cost calculator, the pole barn cost calculator for a garage or outbuilding, or the home addition cost calculator if the deck is part of a bigger project.
Frequently asked questions
How much does a 12 × 12 deck cost?
A 12 × 12 deck is 144 sq ft, with about 36 ft of railing on three open sides. Multiply 144 by your contractor's price per square foot, add the railing by the foot and the stairs, then the permit.
Does my deck need a railing?
Under the residential code, a guard is required where the deck surface is more than 30 inches above the ground within 36 inches of the open edge.[2] Your local code may add to that.
What does a deck cost on average?
The Census Bureau's 2023 housing survey found a median of $4,750 and an average of $8,860 for porch, deck and patio jobs, including do-it-yourself work.[1] Your own price depends on size, height and materials.
Do I need to call before digging deck footings?
Yes. Every state requires a call to the one-call center (811) 48 to 72 hours before digging, and that applies to homeowners.[3]
Sources
- American Housing Survey 2023, Table C-16-OO: Home Improvement Costs, Owner-Occupied Units
- Construction Tip Sheet 03: Residential Guards (Guardrails), 2021 IRC with Washington amendments
- Call Before You Dig (811)
- Publication 936 (2025), Home Mortgage Interest Deduction
- What is the difference between a home equity loan and a home equity line of credit (HELOC)?
- What You Should Know About Home Equity Lines of Credit (HELOC)