Binoculars Range Calculator

Estimate the distance to a target by entering its known height or width and the angular size it subtends on your binoculars' mil-dot or MOA reticle, using the standard mil-relation ranging formula.

Quick Facts

Formula
Range = (Target size × 1000) / Angular size in mils
H and range come out in the same unit; θ must be in mils (small-angle approximation).
Reticle calibration
1 mil ≈ 3.6 in at 100 yd (≈10 cm at 100 m)
The standard mil-dot/MOA spacing used for range estimation through binoculars and rifle scopes.

Your Results

Calculated
Estimated Range
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Distance to target
Range in Yards
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Imperial equivalent
Range in Feet
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Imperial equivalent (short range)
Angular Size (θ)
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Your reading, converted to degrees

Ready

Enter the target's known size and its angular reading, then press Calculate.

About the Binoculars Range Calculator

This tool estimates how far away a target is using nothing but your binoculars' reticle and one known dimension of the target. It is the same "mil-relation" technique used by hunters, birders, surveyors, and military observers for decades: read the angle a target subtends through a mil-dot or MOA reticle, compare it to the target's real-world size, and the distance falls out of a single equation.

Understanding the formula

The calculator applies the mil-relation ranging formula:

Range = (Target size × 1000) / Angular size (mils)

Here, Target size is the actual height or width of the object you're viewing (in meters), and Angular size is how large that same dimension appears through the reticle, measured in milliradians (mils). The formula comes directly from the small-angle approximation: for small angles, angle (radians) ≈ size ÷ distance, so distance ≈ size ÷ angle. Because 1 mil is defined as 1/1000 of a radian, multiplying by 1000 turns that relationship into a distance in the same unit as the target size you entered.

Working with angular units

  • Milliradians (mils) are the most common reticle unit for range estimation; 1 mil subtends roughly 1 meter at a range of 1000 meters.
  • Minutes of arc (MOA) are common on rifle-scope reticles; 1 MOA ≈ 0.291 mils, or about 1.047 inches at 100 yards.
  • Whichever unit your reticle is calibrated in, select it in the "Angular unit" field — the calculator converts it to mils internally before applying the formula.

Knowing the limits

The mil-relation formula assumes you know the target's true size accurately, that the target is roughly perpendicular to your line of sight, and that your reticle reading is steady (a shaking hand or a target that isn't square to you both introduce error). Because range is directly proportional to assumed target size, a 10% error in that size produces roughly a 10% error in the estimated range. At very long distances, atmospheric refraction and the curvature of the earth can also introduce small deviations that this simple formula does not model.

Frequently Asked Questions

How does the mil-relation ranging formula work?
It uses the small-angle approximation: Range = (Target size × 1000) / Angular size in mils. You need one known dimension of the target (its height or width) and the angle it subtends as read off a mil-dot or MOA reticle in the binoculars. Because the angle is small, distance and angular size are inversely proportional, which is why multiplying by 1000 converts a milliradian reading directly into range.
What is the difference between mils and MOA?
Both are units for measuring small angles on a reticle. A milliradian (mil) is 1/1000 of a radian, so 1 mil subtends about 1 meter at 1000 meters. A minute of arc (MOA) is 1/60 of a degree, so 1 MOA subtends about 1.047 inches at 100 yards. One mil equals roughly 3.438 MOA. Use whichever unit matches your binoculars' reticle markings.
How accurate is range estimation with binoculars?
Accuracy depends almost entirely on how precisely you know the target's true size and how carefully you read the angular subtension. Because range is directly proportional to assumed target size, a 10% error in the size estimate produces roughly a 10% error in the calculated range. The method also assumes a flat line of sight and breaks down at very long distances where atmospheric refraction becomes significant.

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