Gutter Calculator
Sixty feet of gutter at a 24 inch example spacing is 31 hangers. A 1,200 square foot roof at 720 square feet per downspout is 2 downspouts, 20.00 feet of leader.
Last updated . Hanger spacing opens at twenty four inches. The 720 is one code cell.
A gutter calculator for the run you measure, the hangers along it, and the leaders. Leader count divides the roof by a square-foot allowance you can replace. The 720 in the box is one IPC table cell.
Metal panels on that roof: metal roof calculator. Gallons the catchment can collect: rainwater harvesting calculator.
Gutter, hangers, and downspouts
720 is one cell of IPC Table 1106.2(1): a 2-inch round leader at 4 inches of rain per hour, as printed on UpCodes. A 2 by 3 rectangular leader at that same rate is 1,380 in Table 1106.2(2). Swap the cell for your leader and your rainfall. Hanger spacing is not taken from the code.
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Length, hangers, and one table cell
The gutter line is the length you measure along the eave. Sixty feet is 18.29 meters. Hangers include a bracket at each end: round the length up by the spacing, then add one. At 24 inches, which is 2 feet, 60 ÷ 2 = 30 and 30 + 1 = 31. That 24 inches is an example spacing, not a maximum copied from a code section.
Downspout count rounds up the horizontally projected roof area divided by the square feet one leader can serve. The box opens at 720 because IPC Table 1106.2(1) lists 720 square feet for a 2-inch circular leader when rainfall is 4 inches per hour. The same table’s 2-inch row is 2,880 at 1 inch per hour, 1,440 at 2, and 960 at 3. Table 1106.2(2) lists a 2 × 3 rectangular leader at 1,380 square feet for that 4 inch rate. Section 1106.1 sizes the system from the 100-year, 1-hour rainfall or other approved local data, so the right cell depends on the leader and the storm, and the field stays editable. At 1,200 square feet and 720, the count is 2. Two leaders at an example 10 feet each are 20.00 feet. The tables are printed at up.codes/s/vertical-conductors-and-leaders.
Worked eave
| Gutter | Spacing | Roof | Allowance | Hangers | Downspouts |
|---|---|---|---|---|---|
| 60 ft | 24 in | 1,200 ft² | 720 | 31 | 2, and 20.00 ft at 10 ft each |
| 60 ft | 24 in | 1,200 ft² | 1,380 | 31 | 1, and 10.00 ft |
Gutter questions
What does the opening gutter order?
Leave the gutter at 60 ft, hanger spacing at 24 in, roof area at 1,200 ft², square feet per downspout at 720, and each downspout at 10 ft. Gutter reads 60.00 ft · 18.29 m. Hangers reads 31. Downspouts reads 2. Downspout linear reads 20.00 ft · 6.10 m.
Why is the allowance 720 square feet?
IPC Table 1106.2(1), as printed on UpCodes, gives a 2-inch circular leader 720 square feet of horizontally projected roof at 4 inches of rain per hour. Section 1106.2 says leaders are sized for that projected area, and 1106.1 points the rainfall rate at the 100-year hour or other approved local data. 720 is that one cell, and the field is there so a different cell can be typed. It is not a rule for every leader and every storm.
What if the leader is a 2 by 3 rectangle?
Table 1106.2(2) lists a 2 × 3 leader at 1,380 square feet for the same 4 inches per hour. Type 1380 in the allowance box and leave the roof at 1,200 ft² and each downspout at 10 ft. Downspouts reads 1. Downspout linear reads 10.00 ft · 3.05 m. Gutter and hangers stay 60.00 ft · 18.29 m and 31.
How are the 31 hangers counted?
Sixty feet divided by 2 feet is 30 spaces. The count includes both ends, so it is 30 + 1 = 31. The 24 inch spacing is an example you type. It is not a code maximum, and this page does not borrow a “so many feet of gutter per leader” rule from a sheet-metal manual.
What if the allowance box is cleared?
Clear the roof-area-per-downspout field and leave the gutter at 60 ft, the spacing at 24 in, and the roof at 1,200. Gutter still reads 60.00 ft · 18.29 m. Hangers still reads 31. Downspouts reads Enter a roof area per downspout. Downspout linear reads —.
What if the hanger spacing is cleared?
Clear the hanger spacing and leave the gutter length. Gutter still reads 60.00 ft · 18.29 m. Hangers reads Enter a hanger spacing. With 720 still in the allowance box, downspouts still reads 2.
What if the downspout length is cleared?
Clear the downspout length and leave 720 and the 1,200 square foot roof. Downspouts still reads 2. Downspout linear reads Enter a downspout length. The gutter line is unchanged.