Is there an easy way to calculate position sizes for trades other than having to solve an equation each time or fire up oanda's profit calculator?

Is there a computer program to do it for you or a position-size calculator? To input the currency pair, total money, and position size (%) and output units to trade? Thanks for any input -

Is there a computer program to do it for you or a position-size calculator? To input the currency pair, total money, and position size (%) and output units to trade? Thanks for any input -