Dutch Betting Calculator: Puntersbook has a standalone dutch betting calculator and with all formulas has integrated dutch betting ability.
The Dutch book is a great way to bet on multiple runners to collect the same amount whichever runner wins. The formula gives you the option to calculate how much to bet on each runner, potential profit and betting options.
Basically the approach is to support 2 or more runners to collect the same amount in one race. If one of the runners wins, then a profit margin can be made. Betting to collect a fixed amount not only increases your potential profit but also reduces losses.