How much to pump for 12 hour trip away?

Alexa • Micah Tyler born 08/31/17 💙
I am going to a concert out of town in a couple weeks by myself and my in laws are watching my son. I read on kellymom that babies get about 25-30 oz a day and I used the milk calculator on there. Should I expect to save about 15-20 oz to be safe? The total time I'll be gone is less than 12 hours.