To determine how many 2×6 boards you need for a 10×10, 12×12, 8×10 & 10×12 deck deck sizes, you’ll need to calculate the total linear footage of the boards required for each deck size.

For a 10×10 deck, you would need 40 linear feet of 2×6 boards (10 feet on each side). For a 12×12 deck, you would need 48 linear feet of 2×6 boards (12 feet on each side). For an 8×10 deck, you would need 36 linear feet of 2×6 boards (8 feet on one side and 10 feet on the other). For a 10×12 deck, you would need 44 linear feet of 2×6 boards (10 feet on one side and 12 feet on the other).

There are different depth of floor joist are used in floor construction such as 2×6, 2×8, 2×10 and 2×12, made of different species of wood (southern yellow pine & Douglas fir) and different grade such as grade – 1, grade – 2, grade – 3. Southern yellow pine is strongest species of wood that can span more distance compared to other species of wood. Grade 1 lumber have higher strength than other grade Lumber due to fewer knots.

Standard joist size use for deck is 2×6 (2 by 6). Others typical floor joist size are 2×4 (2-by-4), 2×8 (2-by-8), 2×10 (2-by-10), 2×12 (2-by-12) and even greater. Most standard, floor joist spacing is 16 inches apart on center, but this can vary depending on building codes and the requirements of the structure. So, 12 inches, 19.2 inches and 24 inches apart on centre are also used.

**How do i figure out how many 2×6 joists i need**

To figure out number of 2×6 joists you would need for a deck, measure the length of subfloor in feet. Multiply the subfloor length in feet by 12 to convert in inches. Then divide it by spacing i.e 24″ or 16″, 19.2″, or 12″ and add 1 in result to get total number of 2×6 joists you needed.

The simple formula to find number of 2×6 joists are following: 2×6 joists count = ((subfloor length × 12)/16) + 1. This equation will help you to figure how many 2×6 joists you needed. For example, if your deck measures 8 by 10 feet, you will need atleast 9 2 by 6 joists which are atleast 10 feet long. i.e (10×12)/ 16) +1 = 7.5 +1 = 8.5, round it as 9.

**How many 2×6 do i need for a 12×12 deck**

A 12-foot x 12-foot deck of 5/4 x 6 pressure treated wood decking on 16 inches on center spacing of joists will require 10 pieces of 2×6 joists. Thus, you will need 10 pieces of 2×6 (2-by-6) beams for your joists, which have to be at least 12 feet long.

Use the formula for floor joists count = ((subfloor length × 12)/16) + 1, and put the span of your deck: joists count = ((12 × 12)/16) + 1 = (144/16) + 1 = 9 + 1 = 10. Thus, you would need atleast 10 pieces of 2 by 6 (2×6) 12 feet long floor joists for a 12×12 deck.

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**How many 2×6 do i need for a 10×10 deck**

A 10-foot x 10-foot deck of 5/4 x 6 pressure treated wood decking on 16 inches on center spacing of joists will require 9 pieces of 2×6 joists. Thus, you will need 9 pieces of 2×6 (2-by-6) beams for your joists, which have to be at least 10 feet long.

Use the formula for floor joists count = ((subfloor length × 12)/16) + 1, and put the span of your deck: joists count = ((10 × 12)/16) + 1 = (120/16) + 1 = 7.5 + 1 = 8.5, round as 9. Thus, you would need atleast 9 pieces of 2 by 6 (2×6) 10 feet long floor joists for a 10×10 deck.

**How many 2×6 do i need for a 10×12 deck**

A 10-foot x 12-foot deck of 5/4 x 6 pressure treated wood decking on 16 inches on center spacing of joists will require 10 pieces of 2×6 joists. Thus, you will need 10 pieces of 2×6 (2-by-6) beams for your joists, which have to be at least 10 feet long.

Use the formula for floor joists count = ((subfloor length × 12)/16) + 1, and put the span of your deck: joists count = ((12 × 12)/16) + 1 = (144/16) + 1 = 9 + 1 = 10. Thus, you would need atleast 10 pieces of 2 by 6 (2×6) 10 feet long floor joists for a 10×12 deck.

**How many 2×6 do i need for a 8×10 deck**

A 8-foot x 10-foot deck of 5/4 x 6 pressure treated wood decking on 16 inches on center spacing of joists will require 9 pieces of 2×6 joists. Thus, you will need 9 pieces of 2×6 (2-by-6) beams for your joists, which have to be at least 8 feet long.

Use the formula for floor joists count = ((subfloor length × 12)/16) + 1, and put the span of your deck: joists count = ((10 × 12)/16) + 1 = (120/16) + 1 = 7.5 + 1 = 8.5, round as 9. Thus, you would need atleast 9 pieces of 2 by 6 (2×6) 8 feet long floor joists for a 8×10 deck.

**How many 2×6 do i need for a 8×12 deck**

A 8-foot x 12-foot deck of 5/4 x 6 pressure treated wood decking on 16 inches on center spacing of joists will require 10 pieces of 2×6 joists. Thus, you will need 10 pieces of 2×6 (2-by-6) beams for your joists, which have to be at least 8 feet long.

Use the formula for floor joists count = ((subfloor length × 12)/16) + 1, and put the span of your deck: joists count = ((12 × 12)/16) + 1 = (144/16) + 1 = 9 + 1 = 10. Thus, you would need atleast 10 pieces of 2 by 6 (2×6) 8 feet long floor joists for a 8×12 deck.

**How many deck boards do i need for a 10×10, 12×12 & 16×16 deck**

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**Conclusions:-**

To figure number of 2×6 joists you would need for a deck, measure the length of deck in inches. Then divide it by spacing i.e 16″ and add 1 in result to get total number of 2×6 joists you needed.