Reticle scale or grid size calculator
  Calculate the required spacing of each division on your reticle based on the expected size of your target and the objective lens that will be used. This will be the "resolution" of your reticle.
  Click the HELP tab above for more detail.
  Calculator - click the "Help" tab above for instructions on use      
  Choose unit of measure
  Enter desired resolution Objective Lens   X
  Reticle division spacing            
  This will be your maximum measurable dimension      
  Enter number of reticle divisions            
  Total scale size    
  This calculator will help you determine which reticle or grid scale to use based on the size of the smallest feature you want to be able to measure. In other words, the desired "resolution" of the reticle.
1 Select your unit of measure.
2 In the "Enter desired resolution" box, enter the smallest dimension you would like to be able to measure. 
3 Enter the magnification of the objective lens you will be using to take this measurement.
4 The "Reticle division spacing" box will show the spacing necessary. This is simply the desired resolution times the objective lens. Note this is the actual dimension on the reticle (the 1x number).
5 To determine the total scale size of a typical reticle with this spacing, enter the number of divisions (usually 50 or 100 or 200, etc.) in the next box. This will tell you the largest dimension you will be able to measure with a particular reticle.
1 You have a stereo microscope that you typically use at the 4x objective lens setting. You want to be able to measure 0.001" increments.
a Select the "Inches" unit of measure.
b Enter .001 in the desired resolution box.
c Enter 4 in the objective lens box.
d The reticle division spacing box displays 0.004 in.
e By entering 100 in the next box, (our PN. S-14283), you can see you will have a total scale of 0.4", which is the maximum dimension you would be able to measure. A 200 division reticle (our PN. S-14310) will have a 0.8" total scale size.
Click the CONSIDERATIONS tab above for more detail.
  Things to keep in mind while using this calculator and selecting a reticle
Results too big or too small:
  While the results displayed will be calculated based on the data input, they will not necessarily make sense.
  You can see by entering a desired resolution of 0.001" and an objective of 40x it will show a division spacing of 0.04". A typical reticle with 50 or 100 divisions would need to be 2" or 4" wide. This would, of course, not fit in a microscope's eyepiece (although we could make the reticle as a special order). You could always get a reticle with smaller spacing, such as 0.01" (our no.'s S-14362, S-14311, etc.) and just count every 4 division lines to measure your feature.
  Another example: you enter a desired resolution of 1 micron and a 5x objective and you get a division spacing of 5 micron. This is too close together considering the typical width of each line on a reticle is 5 micron. It would also be very difficult to see in the eyepiece.
  Also consider that dimensions below 0.2 micron are below the capabilities of optical glass, and 0.2 would be obtainable only under the very best circumstances. For very small features, a suggested expectation would be 0.5 micron and above using a high-power objective.
Scale should fit in the eyepiece field diameter
  Using a desired resolution of 0.01mm and a 20x objective lens results in a 0.2mm spacing. A reticle with 100 divisions (our no. S-14334) has a total scale of 20mm. This will only fit on a reticle with a physical diameter larger than 20mm, and would only be completely visible in a eyepiece with a field diameter (a.k.a. aperture size), larger than 20mm (typically at least 1mm larger). Also, it is usually more difficult to read the scale at the very edges of the visible field. The field diameter number is written on the outside of the eyepiece. E.g. WF10X/18MM means it is a 10X eyepiece with an 18mm field diameter. Note the 18mm does NOT denote the physical diameter of the reticle it will accept. The reticle will be physically larger than the field diameter.
  Of course, if you want the scale or grid to "fall off" the edge of the reticle then simply order a scale larger than the physical or field diameter. We do not require the selected scale/grid to fit on the selected physical diameter.
You can use a scale/grid with a smaller division spacing
  Let's say when you entered your data it came up with a division spacing of 0.008" (our no.'s S-14360, S-14309). It also works to use a scale with a 0.004" spacing (S-14100, S-14283, S-14310, etc.) and just count two lines to measure the feature you need. Why would you want to do this? It may be that 0.004" gives you more flexibility to use other objectives in addition to the one you used for this calculation. Generally, however, a coarser scale is easier to use.
What is "objective" magnification for this calculator?
  This is the total magnification between the reticle's mounting position and the microscope stage. In most configurations this is pretty easy to determine. The reticle is usually at the bottom of the eyepiece, below its lens system (the field lens), so the eyepiece magnification is not considered, and the objective is the lens closest to the target.
  However sometimes there are other considerations:
- on a stereo microscope there may be an additional auxiliary lens attached below the zoom lens system.
- the reticle may mount above one of the eyepiece lenses (in-between its lenses). This is common in higher magnification eyepieces such as 15x or 20x.
- in an example where the reticle is mounted in a 15x eyepiece above a 1.5x field lens, on a stereo microscope in the 4x position, with a 1.5x auxiliary lens attached, the total magnification between the reticle and the stage would be 1.5 x 4 x 1.5 = 9x.
  If the total magnification between the reticle and the target is not known you can measure it by using a stage micrometer and a reticle.