If you’ve ever stood in the lighting aisle of a home improvement store, squinting at the little packages, you’ve probably felt a little lost. For years, we all just grabbed a 60-watt bulb and called it a day. But now, with LED bulbs taking over, the numbers on the box have changed, and the old rules don’t apply anymore. Don’t worry, though. Once you understand two simple terms—lumens and watts—you’ll be able to pick the perfect bulb for every room in your house, every time.

Let’s start with watts. A watt is a measure of how much electricity a bulb uses. Back when incandescent bulbs were the only option, wattage was a rough guide to brightness. A 60-watt incandescent gave off a certain amount of light, and a 100-watt bulb was brighter. But that’s because all incandescent bulbs were about the same efficiency. Today, an LED bulb can produce the same amount of light as a 60-watt incandescent while using only 8 to 12 watts. So if you look only at watts, you might accidentally buy a very dim bulb. That’s where lumens come in.

A lumen is a measure of how much visible light a bulb actually produces. Think of lumens as the “brightness” number. The higher the lumens, the brighter the light. For a standard living room or bedroom, you’ll want a bulb that puts out about 800 lumens, which is roughly equivalent to an old 60-watt incandescent. For a bathroom or kitchen where you need more light for tasks, look for around 1100 lumens, about the same as a 75-watt incandescent. And for a reading lamp or a workshop, 1600 lumens (like a 100-watt incandescent) will give you all the light you need.

But wait—there’s another factor that’s just as important as brightness, and that’s the color of the light. You’ll see this listed as “color temperature” measured in Kelvins. Lower numbers, around 2700K, give off a warm, yellowish glow that feels cozy and relaxing. These are perfect for bedrooms, living rooms, and dining areas. Higher numbers, around 5000K, produce a cool, bluish-white light that feels energizing and crisp. Those are better suited for garages, workshops, and laundry rooms where you want to see details clearly. In between, 3000K to 4000K gives a neutral white light that works well in kitchens, bathrooms, and offices.

Now, you might be wondering about those “soft white” and “daylight” labels on the packages. “Soft white” usually means 2700K to 3000K, and “daylight” is typically 5000K to 6500K. Keep in mind that “daylight” bulbs can feel harsh indoors, so use them sparingly in living spaces.

Another term you’ll see is “CRI,” which stands for Color Rendering Index. This measures how accurately a light source shows the true colors of objects compared to natural sunlight. A CRI of 80 or above is good for most homes. If you’re doing detail work, like painting or sewing, look for a CRI of 90 or higher. It makes a noticeable difference, especially when you’re trying to match colors.

So, when you’re standing in front of that wall of bulbs, here’s your cheat sheet. First, decide how bright you want the room. For a regular lamp, shoot for 800 lumens. For a brighter area, go for 1100 or 1600. Then, pick the color temperature based on the mood you want. Warm for cozy, cool for task lighting. Finally, check the label for the estimated yearly energy cost. LEDs use so little electricity that even a bulb that’s on for several hours a day might only cost a few dollars per year. That’s money you can spend on other home projects.

One more thing to keep in mind: not all LED bulbs are dimmable. If you have a dimmer switch, look for the word “dimmable” on the package. Even then, some dimmable LEDs can buzz or flicker with older dimmers. If that happens, try replacing the dimmer switch with one that’s designed for LED bulbs. It’s a small upgrade that makes a big difference.

You might also notice that some bulbs say “warm dim” or “dim to warm.” These special bulbs actually change color as you dim them, getting warmer and cozier, just like old incandescent bulbs used to. They’re a treat for your favorite reading lamp or a dining room chandelier.

The bottom line is this: forget about watts. Look for lumens to get the brightness you want, and Kelvins to get the color you want. Once you start using this simple system, you’ll never grab the wrong bulb again. And you’ll probably save some money on your electric bill too, because LEDs last years longer than incandescent or halogen bulbs. So go ahead, brighten up your home the smart way, and enjoy the perfect light for every room.