What Binocular Numbers Like 8x42 Mean
In 8x42, the 8 is the magnification and the 42 is each front lens width in millimeters; 42 divided by 8 gives the exit pupil, a guide to dim-light brightness.
By Adolph GreenContributing writer.
On this page
The short answer
Binoculars carry two numbers, such as 8x42 or 10x50.
- The first number is the magnification. An 8x binocular makes things look eight times closer.
- The second number is the objective lens diameter in millimeters. That is the width of each of the two big lenses at the front, the ones farthest from your eyes. A wider lens gathers more light.
So 8x42 means eight times magnification with 42 mm front lenses.
Magnification: more detail, more shake
Nikon explains the trade-off this way: higher magnification shows more detail at a distance, but it also magnifies the shake of your hands, so very high power models may need a tripod. Lower magnification gives a wider view and is easier to hold steady, which helps with moving subjects such as birds in flight or sports.
On Wiki Shopping, 67 binoculars are 10x, 59 are 8x or less, 29 are 12x to 16x and 16 are 20x or more.
Lens size: brightness vs weight
Larger front lenses do better in dim light but make the binocular heavier. Smaller lenses keep it light and easy to carry.
| Lens size on Wiki Shopping | Binoculars |
|---|---|
| Under 32 mm | 50 |
| 32 to 42 mm | 77 |
| Over 42 mm | 45 |
If weight matters most, 60 listings on Wiki Shopping are marked compact.
Exit pupil: the math behind brightness
Divide the second number by the first and you get the exit pupil, the width in millimeters of the beam of light that leaves each eyepiece. For an 8x42, that is 42 divided by 8, or 5.25 mm. Makers round it on their spec sheets; Leupold lists 5.2 mm for one of its 8x42 models.
Nikon says the view is brightest when the exit pupil is at least as wide as your own pupil. Your pupils open to about 6 to 7 mm in low light, so a larger exit pupil helps at dawn and dusk.
| Binocular | Exit pupil |
|---|---|
| 8x42 | 5.25 mm |
| 10x42 | 4.2 mm |
| 10x50 | 5 mm |
| 8x25 | 3.1 mm |
Field of view
Field of view is how wide a scene you see. It is given either as a width in feet at 1,000 yards or in degrees; Nikon's example is 330 feet at 1,000 yards, or 6 degrees. A wider view makes it easier to find and follow a moving subject. Lower magnification usually means a wider view.
Matching the numbers to your use
- Birding and nature: a wide view and steady image help you follow movement. 76 binoculars on Wiki Shopping are listed for birding.
- Hunting and low light: a bigger exit pupil helps at dawn and dusk. 45 are listed for hunting.
- Travel and hiking: smaller lenses keep weight down.
- Wet weather: 73 binoculars are listed as waterproof and 29 as fogproof.
How we count
Magnification, lens size and features are read from each binocular's store listing. Of the 213 binoculars listed on October 26, 2026, 171 fall in the magnification groups above; the rest are left out of that count. Exit pupil values are our own division of the two numbers. Counts change as listings are added or removed.
Shop by spec
Binoculars
12x to 16x, Over 42 mm
- POWERFUL 15X MAGNIFICATION: Giant astronomy binoculars with massive 70mm objective lenses and 20x power. Pair them with any tripod for long-distance land-based viewing or astronomical observation.
- WORKS WITH YOUR TRIPOD: Due to their size & weight, most users mount SkyMaster binoculars on a traditional photo tripod (not included). The built-in ¼”-20 adapter attaches to most tripods in seconds.
- BRIGHT, SHARP VIEWS WITH BaK-4 PRISMS: The SkyMaster is a favorite among those who view in dim conditions near dawn and dusk or at night for astronomy. BaK-4 prisms maximize light throughput to your eye so you see brighter, more detailed images.
- DURABLE AND WATER-RESISTANT: A rubber-armored housing protects your binoculars from damage and provides a secure gripping surface. The water-resistant exterior stands up to tough conditions and unexpected rainy weather.
- UNBEATABLE WARRANTY & CUSTOMER SUPPORT: Buy with confidence from Celestron, a leading optics brand in California since 1960. Your purchase includes a Celestron Limited Lifetime US Warranty & US-based expert tech support.
12x to 16x, Over 42 mm, Porro
- Item number: Tas170125
- Made in : China
- Package weight: 1.429 kg
- Product type: BINOCULAR
10x, 32 to 42 mm
- READY FOR ANY ADVENTURE: The Outland X 10x42 delivers bright, detailed views in a lightweight, pocket-friendly design-perfect for birdwatching, hiking trails, or spontaneous outdoor outings.
- 10X MAGNIFICATION: Spot distant wildlife, birds, and landscapes with ease. The 10x power delivers detailed views while maintaining a steady image-ideal for tracking movement without losing clarity.
- 42MM OBJECTIVE LENS: 42mm lenses deliver bright, high-contrast views in a compact design-perfect for the trail, the park, or wherever your adventures take you.
- BRIGHT, TRUE-TO-LIFE VIEWS: Multi-coated lenses boost light transmission to your eye, while high-quality BaK-4 prisms produce sharp, color-accurate images in a variety of lighting conditions.
- RUGGED, WEATHER-READY BUILD: Rubber-armored polycarbonate housing shields against bumps and drops. Waterproof and nitrogen-purged to prevent fogging in rain, snow, or humidity.
- TRIPOD-ADAPTABLE FOR STABLE VIEWING: Designed with built-in tripod adapter threads so you can mount the binoculars on a standard tripod (adapter not included) for shake-free, extended viewing sessions.
- 5.5° ANGULAR FIELD OF VIEW: Great for tracking wildlife and scanning broad areas-follow moving subjects with ease while keeping more of the landscape in view.
- UNBEATABLE WARRANTY & CUSTOMER SUPPORT: Buy with confidence from Celestron, a leading optics brand in California since 1960. Your purchase includes a Celestron Limited Lifetime US Warranty & US-based expert tech support.
8x or less, 32 to 42 mm
- THE PERFECT BINOCULARS FOR EVERY ADVENTURE: Nature DX 8x42 offers sharp, detailed views in a compact, lightweight frame-ideal for birdwatching, hiking, and everyday adventures.
- 8X MAGNIFICATION: Get detailed views of birds, wildlife, and distant landscapes. 8x power strikes the perfect balance between image stability and the ability to spot fine features from afar.
- 42MM OBJECTIVES LENS: Compact yet capable, the 42mm lenses offer a balance of portability and bright, detailed views for outdoor adventures.
- BRIGHT, SHARP, TRUE-TO-LIFE VIEWS: Fully multi-coated lenses maximize light transmission, while phase-coated BaK-4 prisms enhance contrast and resolution for crisp, color-accurate images in any lighting.
- RUGGED, WEATHER-READY BUILD: The rubber-armored polycarbonate housing shields against bumps and drops. It’s also waterproof and nitrogen-purged to resist fogging in rain, snow, or humidity.
- TRIPOD-ADAPTABLE FOR STABLE VIEWING: Designed with a built-in tripod adapter socket so you can mount the binoculars on a standard tripod (adapter not included) for shake-free, extended viewing sessions.
- WIDE 7.4° ANGULAR FIELD OF VIEW: Track movement with ease, scan open landscapes and spotting birds in flight.
- UNBEATABLE WARRANTY & CUSTOMER SUPPORT: Buy with confidence from Celestron, a leading optics brand in California since 1960. Your purchase includes a Celestron Limited Lifetime US Warranty & US-based expert tech support.