Insulation & Lumber Calculators
Insulation depth is target R-value ÷ R per inch. Reaching R-49 with blown cellulose at about R-3.5 per inch takes 14 in. Lumber is priced by the board foot, thickness × width (in) × length (ft) ÷ 12, and walls are framed by stud count, all covered below.
Insulation Calculator
Depth and volume of insulation to hit a target R-value.
Board Foot Calculator
Board feet of lumber and total cost.
Stud Calculator
Studs and plates to frame a wall at 16 or 24 in centers.
Framing and energy
Wood framing and thermal performance are linked: stud size limits cavity depth, cavity depth limits batt R-value, and spacing sets batt width. Lumber pricing also differs by trade. Big-box stores price framing by the piece, while hardwood dealers quote by the board foot. Use these tools together when you finish an attic, build a partition or plan a woodworking project, and check climate-zone recommendations before buying insulation.
Which calculator do I need?
- Insulation: how thick a layer must be to reach a target R-value, plus loose-fill volume.
- Board foot: pricing rough hardwood or comparing lumber quotes by volume.
- Stud: counting studs and plates for a new wall at 16 or 24 in on center.
A typical sequence for finishing an unfinished room is to frame any new walls first, run electrical and plumbing, have rough-in inspections done, then insulate walls and ceiling before hanging drywall. Use the stud tool for the framing order, the insulation tool for each cavity type, and the board foot tool if you are buying hardwood for built-ins, shelving or trim afterward.
Before you buy
Seal air leaks in the attic floor and around rim joists before adding insulation, since moving air bypasses even thick layers. Install baffles at the eaves so soffit vents stay open. Sight down every stud at the yard and reject badly bowed or twisted pieces. When buying hardwood, ask whether prices are for rough or surfaced boards, and add extra for defects you will cut away. Check for utility rebates and federal tax credits on qualifying insulation upgrades, and keep the receipts and product labels for any claim you file.
Frequently asked questions
What R-value do I need in my attic?
ENERGY STAR recommends R-30 to R-60 depending on climate zone.
Is a 2×4 really 2 by 4 inches?
No. A dry, dressed 2×4 is 1.5 × 3.5 in.
What batt width fits 16 in studs?
Batts for 16 in on-center framing are about 15 in wide; 24 in framing uses 23 in batts.
How many board feet is a 2×4×8?
About 5.33 board feet using nominal dimensions.