Flagpole Wind Load Calculator

Verify a flagpole against the wind load at its installation site using ANSI/NAAMM FP 1001-07.

This calculator follows the procedure in NAAMM/FP 1001-07, Guide Specifications for Design of Metal Flagpoles. Enter the wind speed at the site and the pole geometry, and we'll walk through each calculation — wind pressure on the pole, flag drag, bending moments, shear, axial load, stresses, and the final Combined Stress Ratio (CSR). If CSR < 1.0, the design is within the allowable limits.

What's covered

  1. Inputs
  2. Wind pressure on the pole (Eq. 1, 2, 3, 6, 7)
  3. Flag wind load (Eq. 4 / 5, 9)
  4. Total bending moment & shear (Eq. 12, 15)
  5. Axial load
  6. Section properties at the base
  7. Calculated stresses (Eq. 21, 22, 23)
  8. Allowable stresses (Eq. 27, Table 6.8.2)
  9. Combined Stress Ratio (Eq. 25, 26)

Inputs

Pick from our catalog (optional)

Select a flagpole from our catalog to pre-fill the geometry below. The pole's manufacturer-certified wind ratings will also be shown for comparison with the calculator's CSR result.

    Manufacturer-certified wind ratings:

      Wind Speed

      We'll look up the 3-second gust wind speed (VASD) for your site.

      Pole Geometry

      Height above ground.
      Straight base section. 0 for a fully tapered pole.

      Flag

      Vertical dimension at the hoist.
      Horizontal dimension (the fly).
      NAAMM allows up to 15 ft. Smaller segments produce a more accurate centroid integration.
      NAAMM Appendix A uses 10%.

      Fill in the inputs above and click Calculate to see the step-by-step calculations.

      Wind Pressure on the Pole

      The pole is divided into segments. For each segment we compute the average diameter, projected area, the height-adjusted wind pressure at its centroid, the drag coefficient, the wind force, and the bending moment about the pole base.

      Formulas

      • Wind pressure (Eq. 1):   P = 0.00256 · V2 · Cd · Ch · G
        • Where:
          • P = Wind pressure in pounds per square foot
          • V = 3-sec gust wind speed in miles per hour
          • Cd = Drag Coefficient
          • Ch = Coefficient for height above ground for wind pressure
          • G = Gust Effect Factor. Use minimum value of 1.14.
          • z = Height above grade
      • Coefficient of height (Eq. 2):   Ch = 2.01 · (z/900)2/9.5 for z > 16.4 ft; otherwise 0.86
      • Drag coefficient (Table 3.2.4):
        • Cd = 1.10   if V·d ≤ 39
        • Cd = 129 / (V·d)1.3   if 39 < V·d < 78
        • Cd = 0.45   if V·d ≥ 78
      • Wind force on segment (Eq. 3):   Wp = P · A · Cd
        • Where:
          • P = Wind pressure in pounds per square foot
          • A is in square feet
      • Bending moment of segment (Eq. 6):   M = Wp · L
        • Where:
          • M = Bending moment of segment
          • Wp = Wind force on segment (Eq. 3)
          • L = Distance from ground surface to the assumed centroid of the segment.
      • Wind Speed x Diameter:   V · d
        • Where:
          • V = Wind speed in mph
          • d = Diameter of cylindrical pole or segment or average diameter of tapered pole or segment in feet

      Constants used: V is the 3-second gust wind speed (mph), G = 1.14 (gust effect factor), z is the centroid height (ft), L is the centroid distance from the base (ft), d is the segment's average diameter (ft), A is the projected area = d · segment length (sq ft).

      # Segment z (ft) Length of Segment (ft) Distance to Centroid L (ft) Avg Pole Dia. d (ft) Area of Segment A (sq ft) Wind Speed x Diameter V · d Drag Coefficient Cd Coefficient For Height Ch Wind Pressure P (psf) Wind Force on Segments Wp (lbf) Bending Moments Mp (lbf·ft)
      Total (Eq. 7):

      Flag Wind Load

      Total Bending Moment & Shear

      Axial Load (DP)

      Section Properties at the Base

      Calculated Stresses

      Allowable Stresses

      Combined Stress Ratio