We reached out to a customer service rep, and they said that for our 3-by-6-inch subway tile with a 0.25-inch grout line, one 8-ounce bottle of Polyblend Grout Renew should be good for about 75 ...

Available in sanded and non-sanded versions, Polyblend Plus accommodates joints up to 1/8-in. (3mm) and meets ANSI A118.7.