Ballistics reference
Reticle Subtension Chart
Quick answer
A mil reticle's smallest common mark, 0.1 mil, covers 0.36 inches at 100 yards and 3.6 inches at 1,000 yards. A 1 MOA reticle line covers 1.05 inches at 100 yards and 10.47 inches at 1,000 yards. In a second focal plane scope, every figure on this page is only true at the single magnification the reticle was calibrated for, almost always maximum power.
Subtension is how much real distance a mark on a reticle covers at a given range. It is what turns a mil dot or a MOA hash mark from a picture into a ranging and holdover tool: read the size of a known target against the reticle, and the subtension tells you the distance, or read distance off a rangefinder and the subtension tells you exactly where to hold.
Both figures below are exact. A milliradian is one thousandth of a radian by definition, so it subtends exactly 3.6 inches at 100 yards with no trigonometry involved. A minute of angle is one sixtieth of a degree, which works out to 1.047 inches at 100 yards by plain trigonometry. Both scale in direct linear proportion to distance, so the whole table is simple multiplication once those two base figures are fixed.
The one condition that changes everything: focal plane. In a first focal plane (FFP) scope the reticle grows and shrinks with the zoom, so every value below is correct at any magnification. In a second focal plane (SFP) scope the reticle stays a fixed size on the glass, so the subtension values are only true at the one power the manufacturer calibrated them for, almost always the top of the zoom range.
What does a mil subtend at each distance?
1 mil covers exactly 3.6 inches at 100 yards and scales linearly, reaching 18 inches at 500 yards and 36 inches at 1,000 yards.
Sourced figure
| Mils | 100 yd | 200 yd | 300 yd | 400 yd | 500 yd | 600 yd | 800 yd | 1,000 yd |
|---|---|---|---|---|---|---|---|---|
| 0.1 | 0.36 | 0.72 | 1.08 | 1.44 | 1.80 | 2.16 | 2.88 | 3.60 |
| 0.2 | 0.72 | 1.44 | 2.16 | 2.88 | 3.60 | 4.32 | 5.76 | 7.20 |
| 0.3 | 1.08 | 2.16 | 3.24 | 4.32 | 5.40 | 6.48 | 8.64 | 10.80 |
| 0.5 | 1.80 | 3.60 | 5.40 | 7.20 | 9.00 | 10.80 | 14.40 | 18.00 |
| 0.8 | 2.88 | 5.76 | 8.64 | 11.52 | 14.40 | 17.28 | 23.04 | 28.80 |
| 1.0 | 3.60 | 7.20 | 10.80 | 14.40 | 18.00 | 21.60 | 28.80 | 36.00 |
| 1.5 | 5.40 | 10.80 | 16.20 | 21.60 | 27.00 | 32.40 | 43.20 | 54.00 |
| 2.0 | 7.20 | 14.40 | 21.60 | 28.80 | 36.00 | 43.20 | 57.60 | 72.00 |
| 3.0 | 10.80 | 21.60 | 32.40 | 43.20 | 54.00 | 64.80 | 86.40 | 108.00 |
| 4.0 | 14.40 | 28.80 | 43.20 | 57.60 | 72.00 | 86.40 | 115.20 | 144.00 |
| 5.0 | 18.00 | 36.00 | 54.00 | 72.00 | 90.00 | 108.00 | 144.00 | 180.00 |
| 6.0 | 21.60 | 43.20 | 64.80 | 86.40 | 108.00 | 129.60 | 172.80 | 216.00 |
| 8.0 | 28.80 | 57.60 | 86.40 | 115.20 | 144.00 | 172.80 | 230.40 | 288.00 |
| 10.0 | 36.00 | 72.00 | 108.00 | 144.00 | 180.00 | 216.00 | 288.00 | 360.00 |
Every figure is exact: mils times distance in yards times 0.036. All units are inches. Metric users multiply mils by metres and divide by 10 for centimetres, an equally exact relationship.
What does a MOA subtend at each distance?
1 MOA covers 1.047 inches at 100 yards, not a rounded 1.000 inch, and the gap between the two grows to 4.72 inches by 1,000 yards.
Sourced figure
| MOA | 100 yd | 200 yd | 300 yd | 400 yd | 500 yd | 600 yd | 800 yd | 1,000 yd |
|---|---|---|---|---|---|---|---|---|
| 0.25 | 0.26 | 0.52 | 0.79 | 1.05 | 1.31 | 1.57 | 2.09 | 2.62 |
| 0.5 | 0.52 | 1.05 | 1.57 | 2.09 | 2.62 | 3.14 | 4.19 | 5.24 |
| 0.75 | 0.79 | 1.57 | 2.36 | 3.14 | 3.93 | 4.71 | 6.28 | 7.85 |
| 1.0 | 1.05 | 2.09 | 3.14 | 4.19 | 5.24 | 6.28 | 8.38 | 10.47 |
| 1.5 | 1.57 | 3.14 | 4.71 | 6.28 | 7.85 | 9.42 | 12.57 | 15.71 |
| 2.0 | 2.09 | 4.19 | 6.28 | 8.38 | 10.47 | 12.57 | 16.76 | 20.94 |
| 3.0 | 3.14 | 6.28 | 9.42 | 12.57 | 15.71 | 18.85 | 25.13 | 31.42 |
| 4.0 | 4.19 | 8.38 | 12.57 | 16.76 | 20.94 | 25.13 | 33.51 | 41.89 |
| 5.0 | 5.24 | 10.47 | 15.71 | 20.94 | 26.18 | 31.42 | 41.89 | 52.36 |
| 7.5 | 7.85 | 15.71 | 23.56 | 31.42 | 39.27 | 47.12 | 62.83 | 78.54 |
| 10.0 | 10.47 | 20.94 | 31.42 | 41.89 | 52.36 | 62.83 | 83.78 | 104.72 |
| 15.0 | 15.71 | 31.42 | 47.12 | 62.83 | 78.54 | 94.25 | 125.66 | 157.08 |
| 20.0 | 20.94 | 41.89 | 62.83 | 83.78 | 104.72 | 125.66 | 167.55 | 209.44 |
Every figure is exact trigonometry: 2 x 3,600 x tan(MOA/120 degrees) x distance/100. Shooters who round 1 MOA to 1.000 inch (the shooter's MOA or IPHY convention) are 4.5 percent small, invisible at 100 yards and a real error by 1,000.
Why does focal plane change how you use these numbers?
A first focal plane reticle physically grows and shrinks as the magnification ring turns, staying in the same proportion to the target at every power. Every value in both tables above applies at any magnification on an FFP scope, which is exactly why FFP is the standard choice for anyone who ranges or holds over at varying zoom, such as Vortex Viper PST Gen II 5-25x50 First Focal Plane Riflescope, EBR-7C MOA.
A second focal plane reticle sits behind the magnifying lens group and stays a fixed size on the glass at every power. Its subtension numbers are correct at exactly one magnification, almost always the top of the scope's zoom range, and wrong at every other setting by a factor equal to how far off that calibrated power the scope is currently set. A scope such as Vortex Strike Eagle 1-6x24 Second Focal Plane Riflescope, BDC3 MOA has holdover marks calibrated at its maximum power; dial the magnification down and every subtension in these tables understates the true value in proportion.
How do I use this chart to range a target?
Measure the target's known size in mils or MOA against the reticle, then find the row for that reading and read across for a size close to the target's actual dimension: the column heading is the range. This is the same relationship the mil and MOA ranging formulas run directly, and the how to read a mil dot reticle guide walks through it with worked examples on real targets.
Sources
- Exact trigonometric derivation of MOA subtension: 2 x 3,600 x tan(1/120 degree)
- Exact definition of the milliradian: one thousandth of a radian, 3.6 inches at 100 yards by definition
Frequently asked questions
What does 1 mil subtend at 100 yards?
Exactly 3.6 inches, by definition, since a milliradian is one thousandth of a radian and 100 yards is 3,600 inches. There is no trigonometry or rounding involved, unlike the MOA figure, which makes 3.6 an exact constant that scales in direct proportion to any distance.
What does 1 MOA subtend at 100 yards?
1.047 inches, from the exact trigonometry of one sixtieth of a degree. Many shooters round this to a flat 1.000 inch, a convention called shooter's MOA or IPHY, which is 4.5 percent small. That gap is invisible at 100 yards and grows to nearly 5 inches of accumulated error by 1,000 yards.
Why does my SFP scope's holdover mark not match this chart?
Because a second focal plane reticle only reads correctly at one specific magnification, almost always the scope's maximum power. At any lower magnification the reticle is smaller on the glass than the values in this chart assume, so the true subtension is larger than these tables show, in direct proportion to how far below maximum power the scope is set.
Is an FFP or SFP reticle better for using a subtension chart?
FFP, if you ever hold or range at more than one magnification, because its reticle subtension is correct at every power without adjustment. SFP works fine if you always shoot at the one power its reticle was calibrated for, typically maximum, and costs less, but using it at any other power without correcting invalidates every number on this chart.
How do I range a target using mil subtension?
Measure the target's known height or width against the reticle in mils, then divide the target's size in yards by that reading and multiply by 1000, then divide by 36 to convert to yards. Equivalently, read straight off this chart: find the row for your measured mil reading and look for the column whose subtension matches the target's real size.
Does reticle subtension change with parallax setting?
No. Parallax affects whether the target image and the reticle sit in the same optical plane, which changes where the reticle appears to point when your eye moves, not the actual angular size of the reticle marks themselves. Subtension is a fixed property of the reticle design and, on SFP scopes, the chosen magnification, independent of the parallax setting.
Researched, not professional advice. This page is compiled from published manufacturer specifications, published optical and ballistic formulas, and owner-review consensus, not hands-on testing. Figures described as a rule of thumb are shooter convention rather than sourced numbers, and they are labelled that way wherever they appear. Ballistic figures come from a point mass model using the ballistic coefficient the maker publishes, so treat them as a starting point and confirm them on paper at a measured distance. Confirm your firearm is unloaded with the action open before you mount, level, torque or bore sight anything. Verify a zero only on a supervised range or a safe, legal backstop, know what lies beyond your target, and follow the law where you hunt and shoot, including rules on land access and permitted cartridges.