The reputable brands of liquid epoxy have data sheets included or available on their site with weight mixing ratios. The best way to mix is to use a paint scal

The reputable brands of liquid epoxy have data sheets included or available on their site with weight mixing ratios. The best way to mix is to use a paint scale (mettler toledo and sartorius make some) which lets you get both amounts precisely. They are made for automotive paints which require very precise ratio measurements (like 30:20:1). Source: I mixed up about 20 gallons of various brands/ratios last year.