To tally or add up some numbers, especially in relation to the cost of something. A noun or pronoun can be used between "tot" and "up." Tot up the various expenses you have during your trip and submit a request for reimbursement from payroll. I nearly fainted when the waiter totted up the bill and told us we owed over $300 for the meal. Let's just tot it all up and divide the cost equally between everyone here.