Light Bulb Shapes & Sizes Guide: A19, ST19, G25, B11, E26, E12 Explained

Navigating the world of light bulbs can feel like learning a secret code. With names like A19, ST19, and G25, and bases like E26 or E12, it's easy to get confused. But understanding these simple designations can unlock the perfect aesthetic and functionality for every lamp and fixture in your home. This ultimate guide will demystify bulb shapes, sizes, and bases, helping you choose the right light every time.

Decoding Light Bulb Shapes: What Do the Letters Mean?

The letter in a bulb's name (like 'A' in A19) describes its general shape, giving you an immediate visual cue about its style and common applications.

1. A-Shape (A19): The Classic Everyday Bulb

• Shape: Resembles the traditional incandescent bulb, featuring a familiar pear-like or spherical shape. The 'A' stands for arbitrary or arbitrary shape, signifying its general purpose.
• Size (A19): The '19' indicates the bulb's diameter at its widest point in eighths of an inch. So, A19 means 19/8 inches or 2 3/8 inches (approximately 60mm).
• Applications: This is your workhorse bulb. Ideal for most household fixtures, ceiling lights, table lamps, floor lamps, and enclosed fixtures where the bulb is hidden. Its diffused light is perfect for general illumination. Many of LafoHome's EcoBright™ Series come in the versatile A19 shape.

2. ST-Shape (ST19): The Vintage Charm of an Edison Bulb

• Shape: 'ST' stands for "Straight Tubular" or "Standard Tubular." These bulbs have a distinct elongated, often teardrop or pear-like shape with a more defined shoulder than A-shapes, reminiscent of early Edison bulbs.
• Size (ST19): Similar to A19, the '19' refers to 19/8 inches (approx. 60mm) in diameter.
• Applications: Perfect for exposed fixtures where the bulb itself is part of the decor. Think industrial pendants, decorative chandeliers, string lights, and wall sconces in vintage or modern farmhouse styles. They are designed to be seen.

3. G-Shape (G25): The Elegant Globe Bulb

• Shape: 'G' stands for "Globe." These bulbs are perfectly spherical, offering a clean, minimalist look.
• Size (G25): The '25' indicates a diameter of 25/8 inches or 3 1/8 inches (approximately 79mm). Other common globe sizes include G16.5 and G30.
• Applications: Commonly used in bathroom vanity strips, pendant lights, and decorative fixtures where a soft, even glow and a stylish appearance are desired. Their uniform shape makes them ideal for visible installations.

4. B & BA-Shape (B11, BA11): The Decorative Candelabra Bulb

• Shape: 'B' stands for "Blunt Tip" (candle shape), and 'BA' stands for "Bent Tip" (candle shape). Both resemble a flame or a candle, designed for elegant, decorative applications.
• Size (B11, BA11): The '11' refers to 11/8 inches or 1 3/8 inches (approximately 35mm) in diameter at their widest point.
• Applications: Primarily found in chandeliers, wall sconces, and decorative fixtures that traditionally used candle flame-shaped bulbs. They add a touch of classic sophistication to any room, often seen in dining areas, entryways, and bedrooms.

Understanding Light Bulb Bases: The Key to Compatibility

The base is the part of the bulb that screws into the socket. Getting this wrong means the bulb won't fit! The 'E' stands for Edison screw, followed by a number indicating the base's diameter in millimeters.

1. E26 Base: The Standard Medium Screw-in Base

• Description: This is the most common screw-in base in North America, often called a "standard" or "medium" base. The '26' refers to its 26mm diameter.
• Common Pairing: You'll find E26 bases on most A19, ST19, and G25 bulbs, as these are typically used in larger, general-purpose fixtures.
• Application: Lamps, ceiling fixtures, outdoor lights, and recessed lighting throughout your home.

2. E12 Base: The Candelabra Screw-in Base

• Description: Known as a "candelabra" base, this is a smaller screw-in base, with '12' indicating its 12mm diameter.
• Common Pairing: E12 bases are typically found on smaller, decorative bulbs like B11 and BA11 (candle shapes).
• Application: Chandeliers, wall sconces, nightlights, and other decorative or accent lighting where a smaller, more delicate bulb is required.

Ready to Choose Your Perfect LafoHome Bulb?

Understanding bulb shapes, sizes, and bases is the first step to truly elevating your home's lighting design. Whether you need the functional brilliance of an A19, the vintage charm of an ST19, the elegant symmetry of a G25, or the delicate flicker of a B11/BA11, LafoHome has a high-quality, flicker-free, and Energy Star certified option for you.