Add up the openings you plan to cut in a cabin sole (two sizes, any count of each) and get the total in square inches and square feet. Use it to price hatch trim and gaskets, to compare layouts, and to see how much of the sole you are about to take away.
Re-doing a cabin sole usually means re-thinking access: a bigger opening over the bilge pump, a second hatch over the keel bolts, a long narrow one over the water tank. Before you draw on a sheet of teak-and-holly plywood, it is worth knowing how much of the panel you are about to remove. The total open area is also what drives the cost of the bits that go around each hole: edge trim, gasket, and the cleats or rabbeted frame that each lid rests on.
Enter the first opening’s length, width and count. If you have a second size, fill in the optional row; leave it at zero otherwise.
Each opening is treated as a rectangle. Rounded corners take off a little: a 1 in corner radius removes about 0.21 in² per corner, which is negligible for planning.
area = L₁ × W₁ × n₁ + L₂ × W₂ × n₂
ft² = in² ÷ 144
Two 18 × 12 in bilge hatches. 18 × 12 × 2 = 432 in², or 3.00 ft².
Add one 24 × 16 in hatch over the tank. 432 + 24 × 16 × 1 = 816 in² = 5.67 ft². On a 4 × 8 ft sheet (32 ft²) that is about 18% of the panel.
Three 14 × 10 in inspection ports and one 20 × 20 in engine access. 14 × 10 × 3 + 20 × 20 × 1 = 820 in² = 5.69 ft².
| Opening | Area (in²) | Area (ft²) | Edge length (in) |
|---|---|---|---|
| 12 × 12 in | 144 | 1.00 | 48 |
| 16 × 12 in | 192 | 1.33 | 56 |
| 18 × 12 in | 216 | 1.50 | 60 |
| 20 × 16 in | 320 | 2.22 | 72 |
| 24 × 16 in | 384 | 2.67 | 80 |
| 24 × 20 in | 480 | 3.33 | 88 |
| 30 × 20 in | 600 | 4.17 | 100 |
Edge length is the perimeter of one opening, which is what you buy in trim, gasket or lip moulding.
Measuring the lid instead of the hole (the lid is larger by the lip on each side). Forgetting the saw kerf when you cut the lid from the piece you remove; if the lid comes from the cut-out, the gap is the kerf width all round and needs a lip or a frame. Entering centimetres in one row and inches in the other.
The calculator assumes rectangles. For a round opening of diameter D, enter length and width as D × 0.886; that square has the same area as the circle.
It only counts when length, width and count are all above zero.
No. It is the clear opening. Add the lip width on each side for the lid size.