The Cost of Floor Joists calculator computes the cost of lumber based on the unit price and the number of joists required for a floor based on the dimension of the room.
INSTRUCTIONS: Choose your preferred units and enter the following:
- (W) Width of Floor across joists
- (L) Length of Floor parallel to the joists
- (oC) On-center separation between joists (default to 16 inches)
- (uP) Unit Price of a floor Joist board
TOTAL PRICE: The calculator computes the number of floor joist boards needed and applies the unit price to compute a total cost in U.S. dollars. However, this can be automatically converted into other currency units (e.g. Pesos) via the pull-down menu.
The Math / Science
ASSUMPTIONS: this algorithm assumes that the following:
- the length of the area is less than or equal to the length of one joist. For spans greater than the length of one joist, a beam is often required and a second row of joists. This would double the number and cost of joists.
- the plate boards are approximately the same size as the joists.
Unit Price (Lumber Prices)
One should always use local pricing for the unit price of a supply like lumber for rafter lumber. However, for convenience, the following prices of 2x6s, 2x8s, 2x10s and 2x12s were observed on the Internet and presented for your convenience
The most recent 2x6 price survey information is:
- Date of Survey: 10/12/21
- Store (online) Surveyed: Lowes
- Price of an 8' 2x6: $6.76
- Price of a 10' 2x6: $10.98
- Price of a 12' 2x6: $11.42
- Price of a 16' 2x6: $17.54
The most recent 2x8 lumber price survey information is:
- Date of Survey: 8/2/22
- Store (online) Surveyed: Menards
- Price of an 8' 2x8: $14.23
- Price of a 10' 2x8: $17.79
- Price of a 12' 2x8: $21.35
- Price of a 16' 2x8: $28.47
The most recent 2x10 lumber price survey information is:
- Date of 2x10 Lumber Price Survey: 8/2/22
- Store (online) Surveyed: Home Depot
- Price of an 8' 2x10: $17.88
- Price of a 10' 2x10: $24.27
- Price of a 12' 2x10: $28.98
- Price of a 14' 2x10: $33.25
- Price of a 16' 2x10: $37.27
The most recent 2x12 lumber price survey information is:
- Date of 2x12 Lumber Price Survey: 8/2/22
- Store (online) Surveyed: Menards
- Price of a 12' 2x12: $39.15
- Price of a 14' 2x12: $46.27
- Price of a 16' 2x12: $53.39
- Price of an 18' 2x12: $71.19
- Price of a 20' 2x12: $90.77
Deck Builder Calculators
- Deck Board Count: Computes the number of decking boards needed for your deck based on the size of the deck and a selection from standard deck board sizes (see below).
- Flooring Material Cost: Computes the cost of flooring based on the total area and unit pricing (e.g. $2.56 per ft2).
- Sub-floor Sheets: Computes the number of 4x8 sheets to cover floor/deck area.
- Sub-floor Cost: Computes the cost of 4x8 sheets to cover fool/deck area.
- Deck Joist Count: Computes the number of floor joists needed for a deck. It returns the number of joists and plate boards, square feet of area and the length of the diagonal.
- Deck Joist Cost: Computes the total cost of the floor joist boards.
Building Calculators
- Area of a Roof
- Pitch of a Roof
- Number of Trusses Needed for a Roof
- 4x8s needed for a roof
- Shingles needed for a roof
- Number and Length of Metal Roof Panels
- Number and Length of Purlins
- Number and Length of Rafters
- Number and Length of Rafter and Collar ties