While determining how many lights you might need for your tree largely comes down to personal taste in density of the lights, linear applications and installations (such as rooflines, railings, and around windows) are much less subjective in determining how many bulbs you will need, and is much more a matter of the spacing of the sockets on your wire. The total number of bulbs needed can be easily determined using the following steps.
First, calculate the total linear feet of string you will need by measuring along each surface you intend to decorate.
Tru-Tone Bulbs are sold in quantities of 25. Once you have determined how many bulbs you need, we recommend rounding up to the nearest multiple of 25. If you find you are only a few bulbs short, 5-Packs of our C7 and C9 bulbs are available in all colors and color mixes.
All Tru-Tone Light Strings have 12 inch spacing between the sockets, so the number of bulbs you need is equal to the measured distance in feet if you are using our light strings. If your light strings have different socket spacing, read on.
For socket spacing other than 12 inch (such as 6 inch or 18 inch) simply convert your measured distance (in feet) to inches by multiplying by 12, then divide that number by the length of your socket spacing to determine how many bulbs you will need (see our example below).
EXAMPLE: If you have 21 feet of roofline to decorate, and your light strings have 8 inch spacing, your calculations would look like this:
First, convert 21 feet to inches: 21 x 12 = 252 inches
Then, divide by the spacing of your sockets: 252 inches ÷ 8 inches = 31.5
Finally, round up to the nearest whole number: 32 bulbs
So you will need about 32 bulbs for this roofline installation. You can buy two 25-count boxes to get 50 bulbs, or one 25-count box and two 5-packs to get 35 bulbs.
It's worth noting that 12 inch spacing is the most common for linear installations, and what most commercial light strings will use too, though commercial light strings are available with both tighter (9 inch, for example) and looser spacing (18 inch, for example).
With tighter spacing, the individual bulbs can begin to lose some of their individuality, creating more of a solid line effect rather than individual points. With looser spacing, it can feel like you don't have enough light coverage and the gaps between the bulbs can seem especially dark when illuminated at night.
A note about large installations
Tru-Tone Classic Light Strings have a decorative vintage style and are largely intended for use where they can be seen and appreciated up close, such as on a tree. While our Classic Light Strings can be used outdoors, for longer outdoor runs or for lights that will be seen from a distance such as rooflines and large outdoor trees, we actually recommend and encourage our customers to use standard, commercially available SPT-1 paired-wire light strings (illustrated below) that come in a variety of lengths and spacing, and can even be purchased on bulk spools and cut to size to create the exact-right light string for your roofline or other installation.
If you used our 25-count light strings on a larger installation, you would have male and female sockets joining together approximately every 25 feet and would have to hide or otherwise manage the extra wire for the lead-ins and tails.
With commercially available light string, you are able to have far fewer connection points, which can reduce the likelihood of problems with poor connections, precipitation issues, or shorting – not to mention an overall neater look.