Free calculator
Flood Cut Drywall Calculator for Water Damage
Free flood cut calculator: drywall area and sheets to remove and replace for a 2 ft or 4 ft cut, by room perimeter.
Feet, or feet and inches: 12, 12.5, 12' 6".
Cut height, from the floor
Add the widths of the doorways in these rooms; there's no drywall there.
Result
Drywall to remove and replace
262sq ft
131.0 linear ft of wall cut at 2.0 ft
- Room perimeters
- 140.0 ft
- Less door openings
- −9.0 ft
- Linear feet cut
- 131.0 ft
- 4×8 sheets (area ÷ 32)
- 9
Each room's walls are counted from inside that room, so a wall between two affected rooms is counted once per side. Add any closets as rooms.
How it's calculated
Flood cut area = (room perimeters − door openings) × cut height, counting each side of a wall separately; 4×8 sheets = area ÷ 32, rounded up. Three rooms with 140 ft of perimeter and 9 ft of doorways, cut at 2 ft: 131 × 2 = 262 sq ft, or 9 sheets.
How to use the flood cut calculator
Enter each affected room's length and width. Choose the cut height measured from the floor (2 ft, 4 ft or a custom height), and enter the total width of the doorways in those rooms, where there's no drywall. The calculator adds the room perimeters, subtracts the openings, and multiplies by the cut height to get the drywall to remove and replace. It also gives the linear feet of cut, which is close to the baseboard you'll pull and reinstall.
Why 2 ft and 4 ft cuts are common
Drywall sheets are 4 ft wide. Hung horizontally, one sheet covers the wall from the floor to 4 ft, so a 4 ft cut is patched with full sheets, and a 2 ft cut with sheets ripped in half lengthwise. Cuts at other heights still work but leave more offcut. Many restoration teams instead set the height from moisture readings: they map how far moisture has wicked up the wall and cut 6–12 in above the highest wet reading, because the visible stain understates how high moisture travels.
| Cut height | Area per 100 linear ft | 4×8 sheets | How a sheet is used |
|---|---|---|---|
| 2 ft | 200 sq ft | 7 (6.25 rounded up) | Ripped into two 2 × 8 ft strips: 16 ft of wall per sheet |
| 4 ft | 400 sq ft | 13 (12.5 rounded up) | Full sheet laid horizontally: 8 ft of wall per sheet |
| 3 ft (custom) | 300 sq ft | 10 (9.4 rounded up) | 3 × 8 ft piece, 1 ft offcut per sheet |
At a 3 ft cut the area ÷ 32 count assumes the 1 ft offcuts get used elsewhere. If they won't, count one sheet per 8 ft of wall instead, the same as a 4 ft cut.
Measuring the affected walls
- Measure each room from the inside. A wall between two wet rooms is counted once from each side.
- Include closets, pantries and short wall returns; they add up quickly.
- Subtract doorways, and cased openings with no drywall. Leave in openings narrower than a foot or so.
- Exterior walls often have insulation behind the drywall. Note those runs separately if wet insulation is being removed.
Room sizes from a floor plan
If there's a floor plan of the property, FloorFigures measures every room's perimeter and wall area from it, free, without another visit to measure. The water damage square footage guide covers floor area and documentation for the rest of the loss.
Updated · FloorFigures
Questions
- What is a flood cut?
- A flood cut is a straight horizontal cut through wet drywall at a set height, with everything below it removed. It opens the wall so the framing and insulation can be checked, removed or dried, and it leaves a clean line for patching in new board.
- How high should a flood cut be?
- Flood cuts are commonly made at a fixed height measured from the floor, usually 2 ft or 4 ft, because those heights line up with 4 ft wide drywall sheets. Another approach is to cut 6–12 inches above the highest wet reading found by moisture mapping, since water wicks up drywall higher than the visible stain shows.
- How do I calculate the square footage of a flood cut?
- Multiply the linear feet of affected wall by the cut height, for each side of each wall. Take each room's perimeter, subtract the door openings, and multiply by the cut height. For example, 131 linear ft cut at 2 ft is 262 square feet of drywall to remove and replace.
- How many sheets of drywall do I need after a flood cut?
- Divide the area by 32 (one 4x8 sheet) and round up. Laid horizontally, a sheet is 4 ft tall, so a 4 ft cut takes one full sheet per 8 ft of wall, and a 2 ft cut takes one sheet ripped into two 2 ft strips per 16 ft of wall. Both give the same count as area ÷ 32. Allow a little extra for corners and short runs.
- Do both sides of an interior wall need a flood cut?
- If water reached both rooms, usually yes, and each side is its own area of drywall. Entering each affected room in this calculator counts the shared wall once from each side, which is the right total. If only one side is wet, enter just the affected room.
Skip the typing. Measure the plan.
Open the floor plan in FloorFigures and every room is measured for you, with the same math per room. Try it free on a sample plan; nothing is uploaded.