This calculator is setup to calculate dry yeast (20 billion cells/gram) needed for 1 gallon of Ale beer.

var og = document.getElementById('og').value;
var wortVolume = 3785; // 1 gallon in ml
var cellsForYeastType = 750000;
var measuredPlato = 259 - (259 / og);
var numCells = parseFloat(cellsForYeastType * wortVolume * measuredPlato) * 0.000000001;
var dryYeastNeeded = Math.round(numCells / 20);