HowManyLights adds up your strands, shows watts and amps, colours the meter green, amber or red and tells you the maximum number of strands of that type for one circuit.
How the calculations work
Tree lights use bulbs per foot of tree height: 50 for a subtle look, 100 for the classic look most stores recommend and 150 for a bright, dense tree. The strand count rounds up to whole strands. Garland is estimated as about three times the height of the tree, which suits a loose spiral.
Outdoor strands add up every run you measured, add ten percent for corners, peaks and the drop to the outlet, and divide by the strand length. Circuit load multiplies strands by watts per strand, converts to amps at 120 volts and compares it with 80 percent of the breaker rating, the usual limit for loads that run for hours. Running cost multiplies the total watts by the hours and days and your electricity price.
Safety reminders
Always follow the maximum number of sets that can be connected end-to-end, printed on the box or tag. Use outdoor-rated cords and GFCI-protected outlets outside, keep connections off the ground and out of puddles, and remember that other appliances on the same circuit count towards the load. When in doubt, ask a licensed electrician.
Private by design
HowManyLights has no server-side processing. Your numbers stay in this browser and are saved in local storage on this device so they are there next time.
Frequently asked questions
How many amps do Christmas lights draw?
A 100-bulb LED mini strand draws about 0.06 A; an incandescent mini strand about 0.33 A.
Is one outlet the same as one circuit?
No. Several outlets often share a circuit, so add up everything on that breaker, including other appliances.
Should I use a GFCI outlet outside?
Yes. Outdoor lights should be plugged into GFCI-protected outlets and outdoor-rated cords.
Is HowManyLights free?
Yes. All four calculators are free with no sign-up.
Are these numbers exact?
They are planning estimates. Check the wattage and end-to-end limits printed on your lights, and ask an electrician if unsure.