How Many Solar Panels Do I Need to Power a House?
A home using 900 kWh a month in a location with 4.5 peak sun hours needs about an 8.2 kW system, or 21 panels of 400 W. Here is the formula and a chart.
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What Size Air Conditioner Do I Need? BTU by Room Size
A 150–250 sq ft room needs about 6,000 BTU, and a 450–550 sq ft room about 12,000 BTU. Here is the full chart and the adjustments that matter.
How Many Deck Boards Do I Need? (12×12, 12×16 and 16×20 Decks)
Divide the deck width by the board width plus gap to get rows, then multiply by the deck length. A 12 × 16 deck needs 29 boards of 16 ft. Chart inside.
How Many Fence Posts Do I Need? (With Corners and Gates)
Divide the fence length by the post spacing, round up and add one. Here is how corners, gates and different spacings change the count, with examples.
Roof Pitch Explained: How to Measure It and Convert to Degrees
Roof pitch is the rise in inches for every 12 inches of run. Here are four ways to measure it, including from the attic, and a pitch-to-degrees chart.
How Many Squares Is My Roof? How to Measure a Roof from the Ground
One roofing square is 100 sq ft. Measure the house footprint with overhangs, multiply by the pitch factor and divide by 100. Chart and examples inside.
How Many Rolls of Wallpaper Do I Need? (With Pattern Repeat)
Count strips, not square feet. Here is the decorator’s method for working out wallpaper rolls, how pattern repeat changes it, and a strips-per-roll chart.
How Many Sheets of Drywall Do I Need for a Room?
A 12 × 12 ft room with 8 ft walls needs 14 sheets of 4 × 8 drywall for the walls, or 19 with the ceiling. Here is the formula, a chart and material estimates.
How Much Paint Do I Need for a Room? (Chart by Room Size)
A 12 × 12 ft room with 8 ft walls needs about 2 gallons of paint for two coats. Here is the formula, a chart for common room sizes and coverage tips.
How Many Tiles Do I Need for a Bathroom Floor or Shower?
Divide the area by the area of one tile plus its grout joint, then add 10–15% for cuts. Worked examples for a bathroom floor, a tub surround and a backsplash.
How to Measure a Room for Flooring (Step-by-Step)
Measure the length and width of each rectangle, add the areas, add 10% for waste and divide by the box coverage. Here is how to handle L-shaped rooms and closets.
How Much Mulch Do I Need? Bags, Yards and Coverage
One cubic yard of mulch covers about 108 sq ft at 3 inches deep, and a 2 cu ft bag covers 8 sq ft. Here is how to work out bags and yards for any bed.