In the general case, where neither the distance nor the object size is known, the formulae may be of little use. In practice, sizes of observed objects are known with reasonable accuracy since they are often people, buildings and vehicles. Using the formulae, distances of the objects can be readily calculated without a calculator. In military terms, distances are of course essential for artillery bombardments and estimations of journey times.
Artillery forward observers are usually trained to estimate the number of mils using combinations of fingers, their fist, and hand held at arm's length.
Many telescopic sights used on rifles have reticles that are marked in angular mils, and these are generally called mil dot scopes. The mil dots serve two purposes, range estimation and trajectory correction. By determining how many angular mils an object of known size subtends, the distance to that object can be estimated with a fair degree of accuracy. Once the distance is known, the drop of the bullet at that range (see external ballistics), converted back into angular mils, can be used to adjust the aiming point. Generally mil dot scopes have both horizontal and vertical crosshairs marked; the horizontal and vertical marks are used for range estimation and the vertical marks for bullet drop compensation. Skilled shooters, however, can also use the horizontal dots to compensate for bullet drift due to wind. Mil dot scopes are most suited for long shots under uncertain conditions, such as those encountered by military snipers and varmint hunters. In both of those cases, the range to the target is not fixed and shots are taken at extreme ranges, so accurate compensation for bullet drop is required.
There are 2000π milliradians (≈ 6283.185 mrad) in a circle. So a milliradian is just over of a circle. Each of the definitions of the angular mil are similar to that value but are easier to divide into many parts.