Building Your own calculator is matter of minutes. It is very intuitive thanks to drag & drop feature. The hardest part can sometimes be to make the right formula. But You don't have to be worried about this. Basically anyone who is familiar with formulas in spreadsheet editor can do it OR You can copy existing calculator and modify formula for Your purpose.
Watch VIDEO below and learn how easy is to build the formula from scratch in calculator that counts up ROI (Return Of Investment). With this calculator users easily find out how much cost they save by purchasing Easy Redmine project management solution.
Here you can check this calculator implementation online:
Formulas used in this ROI calculator
formula 1 = F12330 * F12359 * 3
formula 2 = if( F12330 > 100, 1990, if( F12330 > 25,990,490)) / (F12330 * F12359 * 3)