Below is a calculator for determining your project requirements for sand and seal. The first table can be used to determine approximately how much holeplug you will need to backfill your boreholes. You need to enter the total linear feet of borehole drilling (i.e., holes without wells) and input the auger size. For example if you are planning to drill 5 15ft holes, you would input 75. If you have your numbers in metric, you can convert to feet with the conversion calculator.
Below this, are two calculators for determining your approximate sand and seal requirements for monitoring well installations. There are separate calculators for each one (because the density of sand is different than holeplug). Use the first one to input your total linear feet of screen to be installed, along with the auger and pipe size, while the second one is used for how much riser you anticipate. It should be noted that these calculations are very approximate; you should allow for significant contingency.
* These are the most common sizes we use, other sizes are also available