How do I calculate the right algaecide dose for my pool?

You need to calculate your pool volume first. For rectangular pools: length × width × average depth × 7.5 = gallons. For circular: diameter × diameter × average depth × 5.9. For kidney shapes, use a free online calculator. Then check the algaecide label—most say “1 quart per 10,000 gallons”—and stick to that. Doubling the dose won’t kill more algae; it can foam up your pool or mess with your chlorine.