Measuring & Estimating: Calculators, Diagrams & Guides
5 calculators · 16 diagrams · 1 guides
Every takeoff on this site reduces to four measurements: area (square feet), length (linear feet), volume (cubic yards), and lumber volume (board feet). The four feeder calculators in this hub own those conversions — breaking irregular rooms into rectangles and triangles, converting perimeter and area into trim-ready linear footage, turning area-times-depth into the cubic yards bulk material is sold in, and translating nominal lumber dimensions into the board feet sawyers and hardwood dealers price by.
They are called feeders because the other calculators lean on them: the flooring calculator needs square footage, the fence and trim tools consume linear feet, every bulk-material calculator (mulch, gravel, concrete) is a cubic-yards problem wearing different densities, and the framing and deck tools speak board feet at the lumberyard. Each feeder is linked inline exactly where its parent calculators need the answer.
The diagrams make the geometry honest: shape-breakdown methods for L-shaped and irregular rooms, the perimeter-versus-area distinction that trips up fencing estimates, the volume basis behind a "yard" of material, and the nominal-versus-actual lumber chart (a 2×4 is 1½ by 3½ inches, and board feet are computed from nominal). Free, no signup, and deliberately simple — these are the tools the rest of the site is built on.
Measuring & Estimating calculators
- Square Footage CalculatorFree square footage calculator: add multiple rooms or odd shapes, subtract doors and windows, and convert to sq ft, sq yards, square meters and squares.
- Linear Feet CalculatorFree linear feet calculator: get running feet from a perimeter, a list of runs, or square feet. Subtract openings, see sticks to buy. No signup.
- Slope CalculatorFree slope calculator: convert rise and run to percent grade, degrees, inches per foot, and H:1V ratio — plus total fall over your run. No signup.
- Cubic Yards CalculatorFree cubic yards calculator: turn length, width and depth into cubic yards, cubic feet and concrete bags. Add multiple pours, subtract voids, no signup.
- Board Foot CalculatorFree board foot calculator: build a lumber cut list and get total board feet, MBF, pieces and linear feet. Nominal sizes or custom hardwood, no signup.
Guides & references
Measuring & Estimating · 16 diagrams
- Measuring & Estimating
Cubic yards for a round footing or column — π × radius² × height ÷ 27
A round footing or column is π × radius² × height, ÷ 27 for cubic yards. Measure the form’s inside diameter — a 12-inch tube 4 ft deep is about 0.12 yd³.
- Measuring & Estimating
Square footage of an irregular room — split it into simple shapes and add the areas
You never measure an odd shape directly. Split the room into simple shapes the calculator knows — rectangle, triangle, circle, trapezoid — find each area, and add them. Here an L-shape is 12 × 8 (96 ft²) plus 7 × 6 (42 ft²) = 138 ft².
- Measuring & Estimating
Net area for paint and drywall — subtract doors and windows from the gross wall
The calculator has add sections (rooms, walls, lots) and subtract sections (doors, windows, cutouts). For wall paint and drywall you want the net: a 14 × 8 wall (112 ft²) minus a door (21 ft²) and a window (12 ft²) = 79 ft². For flooring, usually keep the gross.
- Measuring & Estimating
Square feet to square yards, squares, acres, and square meters — the conversion factors
Square feet is the hub — convert to whatever the material is sold in: ÷ 9 for square yards (carpet, ready-mix), ÷ 100 for squares (roofing & siding), × 0.0929 for m², ÷ 43,560 for acres. Worked from 900 ft². Add your waste factor before you order.
- Measuring & Estimating
What a board foot is — the ÷12 lumber formula and 144-cubic-inch definition
A board foot is a volume — one square foot of board, one inch thick (144 in³). Board feet = thickness(in) × width(in) × length(ft) ÷ 12, so a 2×4×8 is 5.33 BF.
- Measuring & Estimating
Board feet uses nominal softwood and rough hardwood size, not the finished size
Figure lumber on its named size — nominal for softwood (a 2×4 is figured 2×4, not 1½×3½; DOC PS 20) and rough quarter thickness for hardwood (4/4 = 1″; NHLA).
- Measuring & Estimating
Board foot vs linear foot vs square foot — three 8-foot boards compared
Same 8-ft length, very different board feet. Linear feet ignore the cross-section and square feet ignore thickness — board feet is the volume, so order hardwood by the board foot.
- Measuring & Estimating
Why a cubic yard is 27 cubic feet, not 3 — the volume formula in feet and inches
A yard is 3 ft, but a cubic yard cubes it: 3 × 3 × 3 = 27 ft³ — not 3. Volume = L × W × depth ÷ 27 (depth in feet), or ft² × depth(in) ÷ 324 (324 = 12 × 27). A 10 × 12 ft slab 4 in thick is 1.48 yd³.
- Measuring & Estimating
Volume take-off — footprint area × its own depth, adding pours and subtracting voids
Every section is a footprint (rectangle, circle, ring, or triangle) times its OWN depth — a slab in inches, a footing in feet. Add the pours, subtract the voids, divide by 27. Round pours use π r² h — enter the diameter, the calculator halves it.
- Measuring & Estimating
Cubic yards to an order — 45 bags a yard, or ready-mix concrete past about 1 cubic yard
Bag yield fixes the count: 27 ft³ ÷ yield → 45 × 80-lb, 60 × 60-lb, or 90 × 40-lb concrete bags a yard (13.5 / 27 / 54 for 2.0 / 1.0 / 0.5 ft³ landscape bags). Under ~1 yd³, bag it; at or above, ready-mix (ASTM C94) or bulk delivery wins.
- Measuring & Estimating
A linear foot is length only — two boards of equal length are equal linear feet
One linear foot = 12 inches of length. A 2″-wide board and a 12″-wide board of the same 8 ft length are both 8 linear feet — width and thickness never count. Buy running-foot goods (trim, fence, gutter) by the linear foot; buy coverage goods by the square foot.
- Measuring & Estimating
Perimeter = 2 × (length + width) — and why baseboard and crown deduct differently
A rectangle’s perimeter is 2 × (length + width): a 14 × 12 ft room is 52 LF. The deduction depends on the trade — baseboard skips a 3 ft doorway (52 − 3 = 49 LF), but crown runs over it and keeps the full 52 LF.
- Measuring & Estimating
Square feet to linear feet of boards — LF = area × 12 ÷ (board width + gap)
A coverage area becomes running feet through the board’s face width: LF = area × 12 ÷ (width + gap). The same 200 ft² is 422 LF of 5½″ deck boards but 686 LF of 3½″ boards — narrower boards need more linear feet. Order decking, flooring, and pickets by the linear foot.
- Measuring & Estimating
One slope, four notations — percent, degrees, inches per foot, and H:1V on one triangle
Every slope notation is rise ÷ run in a different dialect: 6″ over 10 ft is 5%, 2.86°, ⅝″ per foot, and 20H:1V — the same slope. Plumbing specs speak in/ft, ADA speaks percent, grading plans speak H:1V. And percent ≠ degrees: a 100% grade is 45°, not 90°.
- Measuring & Estimating
The string-line method — how a slope becomes a total fall you can stake
A slope only becomes buildable as a total fall: fall = slope × run, so a 1% french drain over 40 ft drops 4.8″ (≈ 4 13/16″). Stake both ends, level a string with a line level, then measure down at both stakes — the outlet must read that much more than the high end.
- Measuring & Estimating
The slope code ladder — drainage minimums and accessibility maximums from 0.2% to 15%
Codes write slopes both directions: drainage slopes are minimums (gutters ≥ 0.2%, french drains ≥ 1%, patios ≥ 2%, foundation grading ≥ 5% per IRC R401.3) while accessibility and driveways are maximums (walkways ≤ 5%, ramps ≤ 1:12 = 8.33% per ADA 405.2, driveways ≤ ~15%). The calculator checks your grade against these presets.
Frequently Asked Questions
How do I calculate square footage of an irregular room?
Break it into rectangles and right triangles, compute each, and add — an L-shaped room is two rectangles; a bay window adds a trapezoid. Measure at floor level along the walls, not across furniture. The square footage calculator handles multi-section rooms and is linked from every calculator that starts with an area. The shape breakdown diagram shows splitting an irregular room into simple shapes.
What is the difference between linear feet and square feet?
Linear feet measure length only — trim, fencing, gutters, and cabinet runs are bought by the running foot regardless of width. Square feet measure area (length × width) for flooring, paint, and siding. Converting between them requires the material width: 120 sq ft of 3-inch flooring is 480 linear feet. The linear feet calculator does both directions. The linear-vs-square-feet diagram shows length-only versus area.
How do I convert square feet to cubic yards?
Multiply area by depth in feet (divide inches by 12), giving cubic feet, then divide by 27. Example: 200 sq ft at 3 inches is 200 × 0.25 = 50 cu ft ÷ 27 ≈ 1.85 cubic yards. The cubic yards calculator runs the conversion for any area shape and is the engine behind all seven bulk-material calculators on the site. The volume take-off diagram shows footprint area × its own depth.
How are board feet calculated?
One board foot is 144 cubic inches of lumber: thickness × width × length (all in inches) ÷ 144 — and by convention you use NOMINAL dimensions, so an 8-foot 2×4 is 5.33 board feet even though its actual section is 1½ by 3½. Hardwood dealers and sawyers price by the board foot; the board foot calculator totals a full cut list. The board-foot diagram shows the ÷12 lumber formula.