DIYer's Quick Reference
Common Conversions:
- 1 gallon = 3.785 liters
- 1 sq ft = 0.0929 sq meters
- 1 inch = 2.54 centimeters
Key Rules:
- Add 10-15% waste for materials
- 1 gal paint ≈ 350 sq ft (1 coat)
- A 2×4 is actually 1.5" × 3.5"
Essential DIY Conversions
Length & Dimensions
- Inches → Centimeters
Furniture, hardware
- Feet → Meters
Room measurements
- Inches → Feet
Project planning
Area & Coverage
- Square Feet → Square Meters
Flooring, paint
- Square Yards → Square Feet
Carpet, sod
- Square Inches → Square Feet
Tile layout
Volume & Capacity
- Gallons → Liters
Paint, stain
- Cubic Feet → Cubic Yards
Mulch, gravel
- Fluid Ounces → Milliliters
Mixing ratios
Paint Coverage Guide
| Paint Type | Coverage (sq ft/gal) | Coats | Metric (m²/gal) |
|---|---|---|---|
| Interior Wall Paint | 350-400 sq ft/gal | 1 coat | 32-37 m²/gal |
| Interior Wall (2 coats) | 175-200 sq ft/gal | 2 coats | 16-19 m²/gal |
| Primer | 200-300 sq ft/gal | 1 coat | 19-28 m²/gal |
| Ceiling Paint | 350-400 sq ft/gal | 1 coat | 32-37 m²/gal |
| Exterior Paint | 250-400 sq ft/gal | Varies by surface | 23-37 m²/gal |
| Trim/Door Paint | 400-500 sq ft/gal | 1 coat (smooth) | 37-46 m²/gal |
How to Calculate Paint Needed:
- Measure room: (Length + Width) × 2 × Height = Total Wall Area
- Subtract doors and windows (~20 sq ft each)
- Divide by coverage rate (350 sq ft/gal for most paints)
- Round up and add one extra gallon for touch-ups
Flooring Material Calculations
| Material | Room Size | Waste Factor | Total to Buy | Note |
|---|---|---|---|---|
| Hardwood (3/4" boards) | 100 sq ft | +10% | 110 sq ft | Standard waste factor |
| Laminate/Vinyl Plank | 100 sq ft | +5-7% | 107 sq ft | Minimal cutting waste |
| Carpet | 100 sq ft | +10% | 110 sq ft | Sold by sq yd, add waste |
| Tile (12" × 12") | 100 sq ft | +10-15% | 115 sq ft | Cuts & breakage |
| Tile (18" × 18") | 100 sq ft | +15-20% | 120 sq ft | Large format, more waste |
| Sheet Vinyl | 100 sq ft | +5% | 105 sq ft | Seamless installs |
Tip: Always round up when purchasing flooring. It's nearly impossible to match dye lots later.
Common Lumber Sizes (Nominal vs. Actual)
| Nominal Size | Actual Size | Common Use |
|---|---|---|
| 1 × 2 | 3/4" × 1-1/2" | Trim, small projects |
| 1 × 3 | 3/4" × 2-1/2" | Trim, shelving |
| 1 × 4 | 3/4" × 3-1/2" | Shelves, trim |
| 1 × 6 | 3/4" × 5-1/2" | Shelving, siding |
| 2 × 4 | 1-1/2" × 3-1/2" | Framing (most common) |
| 2 × 6 | 1-1/2" × 5-1/2" | Deck joists, framing |
| 2 × 8 | 1-1/2" × 7-1/4" | Beams, joists |
| 2 × 10 | 1-1/2" × 9-1/4" | Floor joists, beams |
| 4 × 4 | 3-1/2" × 3-1/2" | Posts, deck supports |
Important: "Nominal" size is what you order, "Actual" size is what you get. Lumber shrinks during drying. Always use actual dimensions in your project plans.
Mulch & Ground Cover Calculations
| Depth | Coverage (per yard) | Volume | Approx. Bags |
|---|---|---|---|
| 2 inches | 162 sq ft | 1 cubic yard | ~13 bags (2 cu ft) |
| 3 inches | 108 sq ft | 1 cubic yard | ~13 bags (2 cu ft) |
| 4 inches | 81 sq ft | 1 cubic yard | ~13 bags (2 cu ft) |
Mulch Calculation Formula:
Cubic Yards = (Length × Width × Depth in inches) ÷ 324
Example: 10 ft × 20 ft × 3 inches = (10 × 20 × 3) ÷ 324 = 1.85 cubic yards
→ Convert Cubic Feet to Cubic YardsHardware Size Conversions
| Item | Imperial | Metric | Use |
|---|---|---|---|
| Screws | #8 × 1-1/4" | 4mm × 32mm | General purpose |
| Screws | #10 × 2" | 5mm × 50mm | Heavier duty |
| Nails | 16d (3-1/2") | 90mm | Framing |
| Nails | 8d (2-1/2") | 64mm | General construction |
| Drill Bits | 1/4" | 6.35mm | Common pilot hole |
| Drill Bits | 3/8" | 9.5mm | Larger holes |
| Pipe (Schedule 40) | 1/2" PVC | ~15mm ID | Plumbing |
| Pipe (Schedule 40) | 3/4" PVC | ~20mm ID | Plumbing |
Pro DIY Tips
Always Buy 10-15% Extra Material
Cuts, mistakes, and pattern matching require extra material. For flooring and tile, 15% waste is standard. For paint, one extra gallon often saves a return trip.
Measure Twice, Cut Once
The oldest DIY rule still holds. Double-check all measurements before cutting expensive materials. Use a quality tape measure and mark clearly.
Calculate Paint by Total Wall Area
Measure room perimeter × height for total wall area. Subtract 20 sq ft per door/window. Divide by coverage rate (usually 350 sq ft/gal for one coat).
Know Actual vs. Nominal Lumber Sizes
A "2×4" is actually 1.5" × 3.5". Always use actual dimensions for calculating project materials and cuts. Nominal sizes are just for ordering.
Convert Tile Size for Coverage Calculations
A 12" × 12" tile = 1 square foot. A 6" × 6" tile = 0.25 sq ft (need 4 per sq ft). Calculate tiles needed: (Area ÷ tile size) + 15% waste.
Account for Grout Lines
Grout lines reduce actual coverage. For large format tiles (18"+), plan for 3/16" grout lines. This affects both material quantities and visual spacing.
DIY Project FAQs
How much paint do I need for a 12 × 12 room?
For a 12' × 12' room with 8' ceilings: (12 + 12 + 12 + 12) × 8 = 384 sq ft. Subtract ~40 sq ft for door and window = 344 sq ft. For 2 coats: 344 ÷ 175 = 2 gallons. Always buy an extra quart for touch-ups.
How many tiles do I need for a 100 sq ft bathroom?
For 12" × 12" tiles: 100 tiles (1 per sq ft). Add 15% for cuts and breakage = 115 tiles. For 6" × 6" tiles: 400 tiles (4 per sq ft) + 15% = 460 tiles. Always round up and buy extra from the same lot to ensure color matching.
What's the difference between nominal and actual lumber size?
Nominal is the name (like 2×4). Actual is the real size (1.5" × 3.5"). Lumber shrinks when dried. The nominal size is what you order, but use actual dimensions for measurements and cuts. This matters for structural calculations and precise fit.