Which binoculars should I buy?

What the two numbers mean, why 8x42 suits most people, and the specifications that matter more than magnification.

Difficulty: beginner
Time: 25 min
Read: 3 min

Short answer

For general use and birdwatching, 8x42 is the standard answer — eight times magnification with 42mm lenses. Higher magnification is harder to hold steady and shows less, not more. Spend on optical quality rather than on a bigger first number.

Binocular marketing pushes magnification, which is the specification that matters least beyond a point. Above about ten times, hand shake makes the view worse rather than better.

Step by step

Understand the two numbers.8x42 means eight times magnification and 42mm objective lenses. The first number is how much closer things look; the second is how much light the binoculars gather, which determines brightness.
Choose 8x for general use.Eight times is the usual recommendation for birds and general outdoor use. It gives a wide field of view, is easy to hold steady, and finds moving subjects far more easily than 10x.
Be cautious about 10x and above.Higher magnification narrows the field of view, magnifies hand shake and dims the image. Anything above 10x realistically needs a tripod, which defeats the point for most uses.
Match the objective size to the use.42mm is the general-purpose choice, bright at dawn and dusk. 32mm is lighter and more portable at some cost in low light. 50mm and above is heavy and mainly for astronomy.
Work out the exit pupil.Divide the objective by the magnification — 42 divided by 8 is 5.25mm. Larger is brighter in poor light. This single number explains most of why 8x42 is brighter than 10x42.
Check the field of view.Quoted in metres at 1,000 metres, or in degrees. A wide field makes finding and following a moving bird much easier, and it is a specification people ignore.
Check close focus if you want insects.Some binoculars focus to two metres, others only to five. It matters a great deal for butterflies, dragonflies and garden watching.
Look at eye relief if you wear glasses.You need long eye relief, around 15mm or more, and twist-down eyecups. Without it you lose a large part of the field of view.
Prioritise optical quality over specification.Coatings, prism type and glass quality determine brightness, contrast and edge sharpness. A good 8x32 beats a poor 10x50 in every practical way.
Try them before buying if you can.Look at something with fine detail and at a high-contrast edge. Check for colour fringing, edge blur and whether the focus wheel is smooth and reachable.
Check the weight honestly.Heavy binoculars stay at home or stay in the bag. Weight is one of the main reasons people stop carrying them.
Buy from a brand with a long warranty.Good binoculars last decades and reputable makers offer long or lifetime guarantees, which makes used ones a reasonable buy too.

Tips

8x42 is the default answer for a reason. Start there unless you have a specific need.
Higher magnification shows less, not more, once hand shake is included.
If you wear glasses, eye relief matters more than any other specification.

Common mistakes

Buying the highest magnification available — Above about 10x, hand shake blurs the image, the field of view narrows so subjects are hard to find, and the image dims. Steadiness matters more than magnification.
Buying very cheap binoculars to see if you like the hobby — Poor optics are dim, blurry towards the edges and tiring to use, which puts people off an activity they would otherwise enjoy. A modest but decent pair is a much fairer test.

If it doesn't work

Image is doubled or gives a headache

Cause: Barrel spacing or dioptre not set, or the binoculars are out of collimation — Fix: Set the spacing and dioptre correctly; if it persists, the prisms are misaligned and need servicing.

Dark ring around the view with glasses on

Cause: Insufficient eye relief or eyecups extended — Fix: Twist the eyecups down and use binoculars with long eye relief.

Cannot hold the view steady

Cause: Magnification too high — Fix: Use 8x, brace your elbows against your body, or lean on something.

Fogged inside after cold weather

Cause: Not nitrogen filled, or seals failed — Fix: Waterproof, nitrogen-purged binoculars prevent this; existing fogging needs servicing.

Questions people ask

What does 8x42 mean?

Eight times magnification and 42mm diameter objective lenses. The first number is how much closer things appear, the second controls how much light gets in and therefore how bright the view is.

Are binoculars for stargazing different?

Somewhat. Astronomy favours larger objectives such as 10x50 for light gathering, and often a tripod. For general use those are heavier than most people want to carry.