Irregular Area

Equal-spacing irregular figure area using the average-ordinate method.

Use consistent units. Formula: A = L[(y1 + yn)/2 + y2 + y3 + ... + y(n-1)]

Inputs

Spacing L (ft)

Add as many equally spaced ordinates as needed (minimum 2).

Station #	Label	Ordinate (ft)	Action

Enter ordinates to draw the figure.

This tool assumes uniform spacing L between each ordinate.
End ordinates y1 and yn are half-weighted; all interior ordinates are full-weighted.
With 10 ordinates, labels map to a through j and match the classic form.
Total area is reported in both square feet and square yards when L and ordinates are entered in feet.

courtensy of Don Uptegraff.