Light-bulb shapes and sizes have changed over the years, making it more difficult to determine which type of light bulb to buy if you're replacing an old one. Luckily, with this handy guide, you'll be able to find the right replacement quickly! It's also important to consider whether or not you need to match your old bulbs' wattage. If so, this guide on LED bulb shapes & sizes will help you pick out the correct wattage as well!
A Series
Introduced in 1902, The A Series shape was standard until 1958. This bulb shape is commonly known as standard or classic shape. It may be hard to find at local hardware stores, but it's easy to find online. The A-series light bulb is small, has a very short neck, and its base is wide enough for both hands to hold while twisting in place. With an average lifespan of 1,200 hours (this might vary depending on wattage), you won't have to change out your bulbs frequently (if ever). You can use them for lamps, ceiling fans, and chandeliers with medium-base sockets that fit up to 60-watt bulbs.
B/C/CA series
The B/C/CA series are designed to fit into BC-style bases. A less common size, they are not as widely available as other styles. On average, these bulbs have a life of about 2,000 hours. When shopping for these types of bulbs, check carefully to ensure that you get them in an appropriate case style.
R & BR Series
The R Series is a low-profile halogen light bulb that is great for recessed downlighting. The R Series features a narrow base, clear glass, and an average life of 2,000 hours. The BR series is similar to the R Series but has a new design and base. This LED light bulb uses 70% less energy than its halogen counterpart and lasts up to 15 times longer. Both of these bulbs come in E26 medium screw bases and E27 standard screw bases, which will fit most applications without requiring any extra hardware or rewiring!
AR & PAR Series
The main difference between these is their shape and base type. The A-series is a line of traditional screw-in incandescent bulbs, while R-series bulbs have a smaller pin base and fit into a reflector socket found in standard household fixtures like ceiling fans and sconces. There are many more shapes than just AR and PAR.
MR Series
MR16/GU10 bulbs are made to replace 35W halogen bulbs. The most popular uses for these lights are in track lighting systems, either on tracks or used with hand-held lighting equipment. Their small size also makes them ideal for applications like shop windows and display cabinets. As they are so small, most people prefer MR16/GU10 LED floodlights over halogen bulbs, as they don't take up as much space and can be mounted closer to what you're trying to illuminate. They also offer high-quality light, something that LED floodlights do better than halogens.
G Series
The G Series light bulbs are known for their long life and low energy consumption. The G Series comes in two types: G-18 has a diameter of 2, is used for table lamps, floor lamps, and small ceiling fixtures. A G-25 has a larger diameter of 21⁄4, ideal for most recessed light fixtures or ceiling lights. They produce 310 lumens with an average life of 15,000 hours. All sizes use a Candelabra base.
Tubes/Tubular (T Series)
Tubular, or tubes, are a common light bulb shape and come in a variety of sizes. The tube's long, narrow shape is useful for fitting into small sockets and confined spaces. Most tubes have two-piece bases that screw together with a small gap between them, meaning they can sometimes be slightly more difficult to fit into an existing fixture. Most tubes have medium-to-long lives that depend on how often they're used.
