How do you keep a running total while grocery shopping?

Add each price the moment the item goes in the cart, not at the end. With a running total you see the budget line coming and can put something back in the aisle instead of at the register.

A method that works

1. Write your budget at the top: say $120.
2. Add each item as you pick it up. For several of the same, multiply: 3 × 2.49.
3. Round up if you want a safety margin.
4. Use the shelf price for the quantity you take, not the “2 for $5” price unless you take two.
5. Before checkout, add tax for taxable items.

Example basket

Item	Entry	Running total
Milk	3.89	3.89
Apples, 3 lb	3 × 1.49	8.36
Bread	4.29	12.65
Coffee	11.99	24.64
Yogurt, 4	4 × 1.25	29.64

Free options

Pen and the back of your list works. So does the iPhone Calculator, if you’re careful to tap + between items; it shows only the last number, so a slip is hard to spot.

Hands-free in the aisle

I build Voice Calculator. You tap the mic once and say “3.89 plus 3 times 1.49 plus 4.29 …” as you shop. Each entry stays on the tape, so you can scroll back to see if bread went in twice, and tap a line to fix it. You can pocket the phone or open your shopping list app: the app keeps listening in the background, and the total sits on the Lock Screen and in the Dynamic Island. Listening stops on its own after 5 minutes of silence.

Related: unit price: which pack is cheaper, how to calculate a discount and the Voice Calculator guides.