If you’ve ever looked at a pair of binoculars, you’ve seen the numbers. But what do numbers on binoculars mean? It’s the most common question new users have. Those figures aren’t just model codes. They are the key specs that tell you exactly what the binoculars can do and if they’re right for your needs. Understanding them is the first step to choosing a great pair.
This guide will explain everything in plain language. You’ll learn how to read the numbers like a pro. We’ll cover magnification, lens size, field of view, and more. By the end, you’ll know exactly what to look for whether you’re birdwatching, at a sports game, or stargazing.
What Do Numbers On Binoculars Mean
The main numbers on binoculars, like “8×42” or “10×50,” are the magnification and the objective lens diameter. They are always listed in that order. The first number is the power. The second number is the size of the front lenses in millimeters. Let’s break down what each one means for you.
Magnification (The First Number)
The number before the “x” is the magnification power. It tells you how many times closer an object will appear compared to your naked eye. An “8x” pair makes things look eight times closer. A “10x” pair makes them look ten times closer.
Higher magnification sounds better, but it has trade-offs. More power means a narrower field of view and shakier image. Your hand movements are also magnified, making the image jittery. Most people find 8x or 10x to be the best balance for general use.
- Low Power (6x to 8x): Wider field of view, brighter image, less shaky. Ideal for birding in woods, sports, theater, and general use.
- Medium Power (10x): Brings subjects closer good for open areas, large fields, some marine use. More hand shake is noticeable.
- High Power (12x and above): Best used on a tripod. Used for astronomy, long-distance wildlife observation, or surveillance.
Objective Lens Diameter (The Second Number)
The number after the “x” is the diameter of the front lenses in millimeters. These are the lenses farthest from your eyes. They gather light. A larger number means bigger lenses that can gather more light, resulting in a brighter image.
Common sizes are 20mm, 32mm, 42mm, and 50mm. A bigger lens usually means a brighter image, especially in low light. But it also means a heavier and larger binocular.
- Compact (20-25mm): Very small and light. Great for pocketing on hikes or at concerts. Image brightness is lower, best for daytime.
- Midsize (28-34mm): A good compromise of size and light gathering. Popular for backpacking and daytime birding.
- Full-Size (40-42mm): The most popular all-around size. Excellent brightness for most situations from dawn to dusk. Manageable weight.
- Large (50mm+): Maximum light gathering for low-light conditions like dawn, dusk, or astronomy. They are heavy and often need a tripod for extended viewing.
Putting It Together: Examples
Let’s look at common configurations:
- 8×42: The classic all-rounder. 8x magnification for a steady, wide view. 42mm lenses for a bright image. Perfect for birdwatching, hiking, and sports.
- 10×42: Similar light gathering as the 8×42, but with more magnification. Great for open areas where you need more reach, like prairie birding or boat watching. The image is shakier.
- 8×32: Lighter and more compact than an 8×42. Slightly dimmer image, but excellent for long hikes or if you prefer less weight.
- 10×50: High power plus large lenses. Good for low-light conditions where you need reach, like deer spotting at dusk. Heavy and shaky without support.
- 7×50: Classic marine binocular. Low power for a steady view on a moving boat. Huge 50mm lenses for a super bright image in murky, dark conditions.
Other Important Numbers and Specs
Besides the main two numbers, you’ll see other terms. These also affect performance and comfort.
Field of View
Field of view (FOV) is how wide an area you can see through the binoculars. It’s usually expressed in two ways: as an angle (e.g., 8.1°) or as a width at a certain distance (e.g., 426ft at 1000yds).
A wider FOV lets you see more of the scene, making it easier to follow moving subjects like birds or players. Generally, lower magnification gives a wider field of view. A wide FOV is very desirable for action viewing.
Exit Pupil
Exit pupil is a calculated number that predicts image brightness. You find it by dividing the objective lens diameter by the magnification. For 8×42 binoculars, the exit pupil is 42 ÷ 8 = 5.25mm.
This number should match the size of your eye’s pupil in the same lighting. In bright light, your pupil is small (2-3mm). At night, it opens to about 7mm. A larger exit pupil (5mm+) gives a brighter, more comfortable image, especially in low light.
Eye Relief
Eye relief is the distance from the eyepiece lens to your eye where you can still see the full field of view. It’s crucial if you wear glasses. Longer eye relief (15mm or more) allows you to see the whole picture with your glasses on. Short eye relief forces you to press your glasses against the lens, which is uncomfortable.
Close Focus
This is the minimum distance at which the binoculars can focus sharply. It’s important for looking at butterflies, flowers, or other close-up subjects. Some binoculars can focus as close as 4-6 feet, while others may only go down to 15-20 feet.
How to Choose the Right Numbers for You
Now that you know what the numbers mean, how do you pick? It depends on your main activity.
For Birdwatching
Most birders prefer 8×42 binoculars. They offer a great mix of brightness, wide field of view (to find birds in foliage), and manageable shake. In open areas like coasts, 10×42 is also popular. Compact 8×32 are a good choice for long walks.
For Hunting and Wildlife
Similar to birding. 8×42 or 10×42 are top choices. For low-light dawn and dusk hunting, a larger exit pupil is key. Consider 8×56 or 10×50 models, but be ready for the extra weight.
For Sports and Concerts
You often don’t need huge magnification. A wide field of view to follow the action is more important. Compact 8×25 or midsize 8×32 are excellent. They are easy to carry and provide a bright enough image in stadium lighting.
For Astronomy
Light gathering is everything. Large 50mm+ objective lenses are standard. Magnification of 10x is common, but higher powers like 15x or 20x are used on tripods. A 10×50 or 12×50 is a great starting pair for stargazing.
For Hiking and General Use
Weight and size matter. An 8×32 or a compact 8×25 will serve you well without being a burden in your pack. The image will be bright for daytime use and the wider field of view is great for scenic viewing.
Understanding the Numbers on the Binoculars Body
Sometimes you see extra letters or codes. Here’s a quick guide:
- CF / IF: Central Focus or Individual Focus. CF means one wheel focuses both barrels. IF means you focus each eyepiece separately (common in marine/military).
- WP / WR: Waterproof or Weather Resistant. WP means they can be submerged (often with nitrogen purging to prevent fogging). WR means they can handle rain but not immersion.
- ED, HD, FL: These refer to special glass (Extra-low Dispersion, Fluorite) that reduces color fringing and increases sharpness and color contrast. They are higher-end features.
- BAK-4 / BK-7: Types of glass used in the prism. BAK-4 is higher quality, providing a rounder, brighter exit pupil. BK-7 is standard and good for most entry-level models.
Common Mistakes When Interpreting the Numbers
Don’t get tripped up. Avoid these common errors:
- Chasing Maximum Magnification: 20x sounds powerful, but without a tripod the image will be a blurry mess. Stick to 10x or 12x for handheld use.
- Ignoring Weight: That 10×50 pair may seem perfect, but if it’s too heavy to hold steady or carry, you won’t use it. Consider how you’ll use them.
- Overlooking Eye Relief: If you wear glasses, always check the eye relief spec. Don’t assume all models will work for you.
- Forgetting the Field of View: Two 8×42 models can have different fields of view. A wider one is generally better for tracking.
Putting Knowledge into Practice: A Simple Checklist
Before you buy, ask yourself these questions:
- What is my primary activity? (e.g., woodland birding, stadium sports).
- Will I use them mostly in daylight or low light?
- Do I wear eyeglasses when viewing?
- How important is size and weight to me?
- What is my budget? (Remember, optics quality matters too, not just numbers).
With your answers, you can narrow it down. For example: “I need a daytime binocular for hiking and occasional birding, I wear glasses, and I want it light.” An 8×32 with long eye relief would be a perfect match.
FAQ Section
What does 10×50 mean on binoculars?
It means 10x magnification and 50mm objective lenses. It brings objects 10 times closer, and the large 50mm lenses gather a lot of light for brighter viewing in low-light conditions.
Which is better, 8×42 or 10×42 binoculars?
Neither is universally better. 8×42 gives a wider view and steadier image. 10×42 brings subjects closer but the view is narrower and shakier. Choose 8x for general use and woods, 10x for open areas where you need more reach.
What do the numbers on binoculars mean for eye relief?
Eye relief is a separate spec listed in millimeters. It tells you how far your eye can be from the eyepiece. Look for 15mm or more if you wear glasses to see the full picture comfortably.
Are higher magnification binoculars better?
Not always. Higher magnification amplifies hand shake, narrows your field of view, and often makes the image dimmer. They are harder to use steadily without support like a tripod.
What does field of view mean on binoculars?
It’s the width of the area you can see through the lenses. It’s like the difference between looking through a window or a tube. A wider field of view makes it easier to locate and follow objects.
What is a good exit pupil size?
For daytime, 2-4mm is fine as your eyes’ pupils are small. For versatile use into low light, aim for an exit pupil of 5mm (like an 8×40 or 10×50). For dedicated low-light use, 7mm is ideal.
Final Thoughts
So, what do numbers on binoculars mean? They are your essential guide to performance. The magnification tells you how close things appear. The objective lens size tells you how bright the image will be. Together with field of view and eye relief, they help you find the perfect tool for your hobby.
The best binoculars are the ones you’ll actually use. Don’t get bogged down by thinking you need the biggest numbers. Balance is key. For most people, a pair like an 8×42 provides that ideal balance of power, brightness, and portability. Now you have the knowledge to look past the numbers and see the perfect pair for your adventures.