Milliradian Calculator
Use this calculator to determine target size, range, or milliradian (mil) value. Enter any two values to calculate the third.
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function calculateMilliradian() {
var targetSizeInput = document.getElementById('targetSizeInches');
var rangeInput = document.getElementById('rangeYards');
var milsInput = document.getElementById('milsValue');
var resultDiv = document.getElementById('result');
var targetSize = parseFloat(targetSizeInput.value);
var range = parseFloat(rangeInput.value);
var mils = parseFloat(milsInput.value);
var filledCount = 0;
if (!isNaN(targetSize) && targetSize > 0) filledCount++;
if (!isNaN(range) && range > 0) filledCount++;
if (!isNaN(mils) && mils > 0) filledCount++;
resultDiv.className = 'calculator-result'; // Reset class
if (filledCount !== 2) {
resultDiv.innerHTML = 'Please enter exactly two positive values to calculate the third.';
resultDiv.classList.add('error');
return;
}
var calculatedValue;
var unitConstant = 1000 / 36; // This constant converts inches/yards to mils (1 mil = 1 inch at 27.778 yards, or 1 yard at 27.778 inches, or 1000 inches at 36000 yards)
// More precisely: Mils = (Target Size in Inches / (Range in Yards * 36)) * 1000
if (isNaN(mils) || mils <= 0) {
// Calculate Mils
if (isNaN(targetSize) || targetSize <= 0 || isNaN(range) || range <= 0) {
resultDiv.innerHTML = 'Invalid input for Target Size or Range. Please enter positive numbers.';
resultDiv.classList.add('error');
return;
}
calculatedValue = (targetSize * 1000) / (range * 36);
milsInput.value = calculatedValue.toFixed(2);
resultDiv.innerHTML = 'Calculated Mils:
' + calculatedValue.toFixed(2) + '';
} else if (isNaN(range) || range <= 0) {
// Calculate Range
if (isNaN(targetSize) || targetSize <= 0 || isNaN(mils) || mils <= 0) {
resultDiv.innerHTML = 'Invalid input for Target Size or Mils. Please enter positive numbers.';
resultDiv.classList.add('error');
return;
}
calculatedValue = (targetSize * 1000) / (mils * 36);
rangeInput.value = calculatedValue.toFixed(2);
resultDiv.innerHTML = 'Calculated Range:
' + calculatedValue.toFixed(2) + ' yards';
} else if (isNaN(targetSize) || targetSize <= 0) {
// Calculate Target Size
if (isNaN(mils) || mils <= 0 || isNaN(range) || range <= 0) {
resultDiv.innerHTML = 'Invalid input for Mils or Range. Please enter positive numbers.';
resultDiv.classList.add('error');
return;
}
calculatedValue = (mils * range * 36) / 1000;
targetSizeInput.value = calculatedValue.toFixed(2);
resultDiv.innerHTML = 'Calculated Target Size:
' + calculatedValue.toFixed(2) + ' inches';
} else {
resultDiv.innerHTML = 'Please leave one field blank to calculate its value.';
resultDiv.classList.add('error');
}
}
Understanding Milliradians (Mils)
A milliradian, commonly shortened to "mil," is a unit of angular measurement widely used in shooting, particularly in long-range precision shooting and artillery. It's a measure of an angle, similar to degrees, but based on radians. Specifically, one milliradian is one-thousandth of a radian (1 mil = 0.001 radians).
The Mil-Dot System and Range Estimation
The practical application of mils in shooting often revolves around the "mil-dot" reticle found in many rifle scopes. These reticles have markings (dots or hash marks) spaced at precise mil intervals. This allows a shooter to:
- Estimate Range: If you know the actual size of a target, you can measure how many mils it subtends in your scope. Using a simple formula, you can then calculate the distance to the target.
- Holdovers/Holdoffs: Once the range is known, or if you need to adjust for bullet drop or wind, you can use mil values to determine how many mils to hold above, below, or to the side of the target without adjusting your scope's turrets.
- Adjust Turrets: Many rifle scopes have turrets that adjust in mil increments (e.g., 0.1 mil per click). This allows for precise adjustments to the point of impact based on calculated mil values.
The Core Formula
The fundamental relationship used in mil calculations is based on the principle that 1 mil subtends 1 unit of length at 1000 units of distance. For example, 1 mil covers 1 meter at 1000 meters, or 1 yard at 1000 yards. When mixing units like inches and yards, a conversion factor is applied.
The formula used in this calculator, relating Target Size (inches), Range (yards), and Mils, is:
Mils = (Target Size in Inches × 1000) / (Range in Yards × 36)
From this, we can derive the other calculations:
Range in Yards = (Target Size in Inches × 1000) / (Mils × 36)Target Size in Inches = (Mils × Range in Yards × 36) / 1000
Practical Examples
Let's look at how this calculator can be used:
Example 1: Estimating Range
You are looking at a target that you know is 18 inches tall (e.g., a standard steel plate). Through your scope, you observe that the target subtends 1.67 mils.
- Target Size: 18 inches
- Mils: 1.67
- Leave Range blank.
The calculator would output: Range: approximately 300 yards.
Example 2: Calculating Holdover/Adjustment
You are shooting at a target 500 yards away. Your ballistic data indicates you need to adjust your point of impact by 36 inches (due to bullet drop and wind).
- Target Size (Adjustment): 36 inches
- Range: 500 yards
- Leave Mils blank.
The calculator would output: Mils: approximately 2.00. This means you would need to hold 2.0 mils high or dial 2.0 mils up on your scope.
Example 3: Determining Target Size
You are at a known distance of 200 yards, and you observe an unknown object that measures 0.5 mils in your scope.
- Range: 200 yards
- Mils: 0.5
- Leave Target Size blank.
The calculator would output: Target Size: approximately 3.60 inches. This could help you identify the object or understand its dimensions.
This milliradian calculator is a valuable tool for shooters and anyone working with angular measurements in a practical context, simplifying complex calculations into quick, actionable results.