Enter the height of the flagpole into the calculator to estimate a recommended flag size for that pole. This calculator uses a common rule of thumb: the flag’s fly (long side) is about 1/4 of the pole height, and it assumes a 3:5 (hoist to fly) flag proportion to estimate the hoist (short side).

Flag Size Calculator

Enter either the flagpole height or the flag fly (length) to calculate the other and the hoist (width).

Flag Size Formula

The following formulas are used to estimate the flag size using a common rule of thumb (fly is about 1/4 of pole height) and an assumed 3:5 flag proportion (hoist:fly). 

FF = PH / 4
FH = FF × 3/5 = PH × 3/20

Variables:

  • FF is the flag fly (length, long side)
  • FH is the flag hoist (width, short side)
  • PH is the flagpole height

To estimate the flag fly (long side), divide the flagpole height by 4. Then estimate the hoist (short side) by multiplying the fly by 3/5 (which corresponds to a 3:5 flag). Note: different flags have different official proportions (ratios), and some situations use a larger or smaller fly-to-pole ratio, so treat these as practical guidelines rather than a universal standard.

What is a Flag Size?

Flag size refers to the dimensions of a flag. The long side is commonly called the fly, and the short side is the hoist. The size of a flag is often chosen in relation to the height of the flagpole on which it will be flown. Proper flag sizing helps the flag look proportionate to the pole and improves visibility.

How to Calculate Flag Size?

The following steps outline how to calculate the Flag Size.

  1. First, determine the height of the flagpole (PH).
  2. Next, estimate the flag fly (long side) using the rule of thumb: FF = PH / 4.
  3. Then, estimate the flag hoist (short side) assuming a 3:5 flag: FH = FF × 3/5 (equivalently, FH = PH × 3/20).
  4. Finally, report the estimated Flag Fly (FF) and Flag Hoist (FH) in your preferred units.
  5. After inserting the variable and calculating the result, check your answer with the calculator above.

Example Problem : 

Use the following variable as an example problem to test your knowledge.

flagpole height (PH) = 20 feet

Estimated flag fly (FF) = PH / 4 = 20 / 4 = 5 feet

Estimated flag hoist (FH) = FF × 3/5 = 5 × 3/5 = 3 feet