Compare magnification, exit pupil, field of view and carrying weight.
Compare up to four binocular specifications. Enter published specifications from the same measurement convention. The calculation describes geometry and an older low-light index, not measured optical quality.
How it works: Exit pupil = objective diameter ÷ magnification. Twilight factor = √(magnification × objective diameter). Linear field width = 2 × distance × tan(angle ÷ 2). One yard is three feet, so feet at 1,000 yards convert to metres at 1,000 metres by dividing by three.
A larger exit pupil can make eye placement easier and may help in dim light if your own pupil is large enough. Twilight factor ignores light transmission, coatings, resolution and your eyesight; it is not a brightness score. A wider field can help follow moving wildlife, while greater magnification can magnify hand shake. Check eye relief with glasses, focus feel, waterproofing and real viewing comfort before choosing.
Instructions
- Replace the sample Model specifications with the binoculars you want to compare.
- Enter Magnification ×, Objective diameter (mm), Field of view, FOV unit and Weight (g). Check the units against the specification sheet.
- Select Compare binoculars. Use Add model or Remove last model to change the list, and Print comparison to keep it.
Understanding your results
An 8 × 42 model has a 5.25 mm exit pupil: 42 divided by 8. Compare that with field width and carrying weight. The numbers can help narrow your choices, but they cannot measure sharpness, coatings or how comfortable the binoculars feel in your hands.
What to do if the field of view looks surprisingly wide or narrow
Check FOV unit. A value in feet at 1,000 yards is different from metres at 1,000 metres or degrees. Compare specifications stated using the same convention and correct any misplaced decimal points.
Using this tool in your browser
This tool handles your entries in your browser with JavaScript enabled and does not save them automatically. Print comparison keeps a paper or browser PDF copy; this calculator has no file-download control. On a phone, your browser controls where downloads go and which print options are available.
Summary
Use the comparison as a starting point, then assess focus, eye relief and real viewing comfort.