How To Determine Rope Light Cutting Intervals

I get lots of questions from people asking if they can cut there rope lights at a specifica length so here is the basic formula to calculate if your desired length of rope light is an even interval of that particular type rope light.
 
1) (Length of the run you want to cut in feet) x (12 inches) This gives you the desired length in inches.
2) (desired length in inches) / (cutting interval) If the result is not a fraction then your length is an interval and can safely be cut at that length.
3) If your result from step 2 is a fraction then you need to adjust your desired length up or down to the correct interval.
 
Here is and example based on 1/2 inch 2-wire 120 volt rope light which is cuttable in 18 inch increments:
 
Cutting interval: 18 inches
Desired length: 111 feet
 
1) 111 feet x 12 inches = 1332 inches.
2) Divide 1332 by 18 and we get exactly 74 (no fraction) so the answer is yes, you can cut a piece exactly 111 feet. Had the result contained a fraction you would have had to make the run longer or shorter. See the example below for a length 1 foot longer:
 

Cutting interval: 18 inches
Desired length: 112 feet
 
1) 112 feet x 12 inches = 1344 inches.
2) Divide 1344 by 18 and we get 74.66666666 A fraction indicates that it is not an interval of 18 inches
3) Now adjust the length up or down to the next closest interval. In this case 74.6666666 is between 74 and 75 total intervals. So the next closest increment is 75 (rounding up) or you might also choose to round down to 74. Then just multiply by the cutting interval to get back to total inches and divide by 12 to get back to feet.
75 x 18 = 1350;  1350/12 = 112.5 feet
74 x 18 = 1332;  1332/12 = 111 feet
So 112 feet would not work, but 112.5 or 111 would.
 
Cutting intervals vary depending on the number of wires and the voltage of your rope light. Most rope light has an icon printed directly on the rope itself to help you determine the correct spot to cut. Cutting intervals should be listed on the retailer's or wholesaler's web site or wherever you are purchasing them. For some good instructions on cutting rope lights click here:
http://www.birddogdistributing.com/rope-light-installation.php

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  Usually there are cutting marks printed on rope lights.  One cutting mark placed 2 ft apart if it's 120V. lower voltages are closer, about 4'' or 8''.

*** cutting marks may misprinted 0.5% of the time, in this case, you should looking for bounding wires which is the wire connects between electrical wires to light bulbs.  cut between two bounding wire will be fine. 

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Something alike was discussed on the Yahoo! Answers last week, i can share a link if you want some