Below are diagrams of the
basic shape of covers for just about any type of spa/hottub.
First 
Review the below diagrams
and determine which cover shape you will need, ie; square,
octagon, circle, etc. Note the type of cover needed.
Second 
This
step is very important !! Make sure and
measure to the OUTSIDE lip of your spa. See diagram
#1. Not the base cabinet, but to the OUTSIDE of
the spa that extends above the base cabinet.
Measurements must be exact
for the cover to fit correctly.
Third 
Make a list of the
measurements you will need. Such as, i.e.; Measurement
A, Measurement B, Measurement C, etc.
Fourth 
Now  Double Check
All of your Measurements. We can't stress this
step enough.
If
done properly, your cover will fit just like the
original. Again, please make sure and follow the above
steps and double check your measurements. Caution  Once a cover
has been ordered, it cannot be changed.
Now,
let's get down to measuring your spa. Use the below
diagram to properly measure your spa.
Diagram # 1
Though the diagram has been altered, it is representative of
what your spa looks like in a cutaway view. Notice,
and we reiterate this again, the measurement is shown as
measuring the outside of the spa itself, NOT the base
cabinet. Using the above diagram as your definitive
guide, onto the cover shape.
There are six (6) basic
cover shapes.....
1. Round
2. Square
or Rectangle
3.
OneCut Corner
4.
TwoCut Corner
5.
FourCut Corner
6.
Octagon
Spa Vertical Extension

or
Not all spas/hottubs extend
the same amount above the deck or cabinet of the spa
unit. Don't forget to include this measurement.
This is also what is called "the skirt".
 How to
Measure A Radius 
Radius Corners
To calculate the radius of a curve on a pool or spa:
Extend two imaginary lines to a point where the sides
would have met had the corner been square.
Provide the distance from the break of the curve (point
A) to the imaginary point (point B). This will be your
radius measurement.
HINT: Use two rulers or 2x4 to extend the sides of your
pool or spa tub to a point (B). This will make it easier to
measure from point A (beginning of radius) to B.
 How To Measure A Cut
Corner 
Hint: Use two rulers to extend the sides of your
spa tub to a point. This will make it easier to measure from
point A to point B.
To provide the information
on a cut corner, it may be necessary to verify the accuracy
of that information.
First, extend two imaginary lines to a point where the
sides would have met had the corner been square.
Check the distance from the inflexion of the cut corner
(point A) to the imaginary (point B).
Now check this measurement against out cut corner
measurement verification chart below.
Cut Corner Spa Cover
Measurement Verification
If
your
cut corner is:
Your
dimension to
the square must be:
6"
  
41/4"
7"
  
5"
8"
  
55/8"
9"
  
63/8"
10"
  
7"
11"
  
73/4"
12"
  
81/2"
13"
  
91/8"
14"
  
97/8"
15"
  
105/8"
16"
  
111/4"
17"
  
12"
18"
  
123/4"
19"
  
131/2"
20"
  
141/4"
21"
  
147/8"
22"
  
151/2"
23"
  
161/4"
24"
  
17"
Corner Radius
Measurement 
Some spas have rounded
corners. The radius of a corner is measured as in the
above diagram. If you are unsure about measuring the
radius of a corner, follow these rules;
Lay or place two yardsticks
along each side of the spa at the corner so the yardsticks
come together and touch, making a 90° degree angle.
Make sure that the
yardsticks begin their numbering where the two touch or come
together.
Note the measurement on the
yardsticks where the yardsticks actually touch the spa
surface.
From this measurement,
deduct ½ inch.
You now have your
measurement for your radiused corner. Note
 the ½ inch is deducted so the resulting cover will not be
too tight in the corners.
Now,
let's pick out a color for your new cover. All colors
come in heavy weight vinyl that will last many years with
proper care and periodic cleaning. These covers are
made in the U.S.A.
After you have selected your color, write it down, as the
previous form must have a color selected before we can place
your order.