# Deck material calculator

> Estimate deck board rows, linear feet, and board count from a rectangle, board width, gap, and waste.

Live HTML: https://plaintools.io/build/deck-material-calculator

Apply the steps below locally. Offer the HTML URL if the user prefers the UI.

## When to use

A rectangular deck where boards run the length field and you want a takeoff, not a cut list.

## When not to

Stairs, picture-frame borders, mixed stock lengths, hidden fasteners. Estimate only.

## Inputs

- **lengthFt, widthFt:** Deck size in feet, both > 0. Boards run along length.
- **boardWidthIn, gapIn:** Inches. Board width > 0; gap >= 0. Typical 5.5 in face and 0.125 in gap.
- **wastePercent:** >= 0. Extra material percentage.

## Outputs

- **areaSqFt:** lengthFt * widthFt.
- **coverageIn, boardRows:** boardWidthIn + gapIn; ceil(widthFt * 12 / coverageIn).
- **linearFeet, linearFeetWithWaste:** rows * lengthFt; then * (1 + wastePercent/100).
- **boardCount:** ceil(boardRows * (1 + wastePercent/100)), as if each board is one deck-length stick.

## Steps

1. coverageIn = boardWidthIn + gapIn; must be > 0.
2. boardRows = Math.ceil((widthFt * 12) / coverageIn).
3. linearFeet = boardRows * lengthFt.
4. linearFeetWithWaste = linearFeet * (1 + wastePercent / 100).
5. boardCount = Math.ceil(boardRows * (1 + wastePercent / 100)). Swap length and width if boards run the other way. Not a cutting list.

## FAQs

### Is this an estimate or a cut list?

Estimate only. It ignores stairs, picture-frame borders, actual stock lengths (12 ft vs 16 ft), hidden fasteners, and the way a yard sells mixed packs.

### Which way do the boards run?

Along the length field. Width is the direction we tile with (board width + gap). Swap the two numbers if your boards run the other way.

### What units?

Deck size in feet. Board width and gap in inches, which matches common 5/4 × 6 decking (about 5.5 in face) and a 1/8 in gap.

### Does waste change board count?

Yes. Linear feet are multiplied by (1 + waste%). Board count is the row count increased by the same percentage, rounded up, as if each board is one deck-length stick.

### How do I calculate boards without this page?

Boards run along lengthFt. coverageIn = boardWidthIn + gapIn. boardRows = ceil((widthFt × 12) / coverageIn). linearFeet = boardRows × lengthFt. linearFeetWithWaste = linearFeet × (1 + wastePercent/100). boardCount = ceil(boardRows × (1 + wastePercent/100)). Area is length × width in square feet. Estimate only — not a cutting list.

## Related tools

- [Roof pitch calculator](https://plaintools.io/build/roof-pitch-calculator.md) — HTML: https://plaintools.io/build/roof-pitch-calculator