Unit-Price Ninja: grocery math that saves real money (with a “cents per ounce” table)
Fin’s quick story
Last month I reached for my usual pasta sauce. New “Family Size!” sticker, same price. Looked bigger… until I checked the fine print: 22 oz down from 24 oz. The “deal” wasn’t a deal—just shrinkflation in a hoodie. That’s when unit-price ninja mode pays off.
The one formula
Unit price = price ÷ size (normalize to the same unit)
- Weight: oz (1 lb = 16 oz; 1 kg ≈ 35.274 oz)
- Volume: fl oz (1 L ≈ 33.814 fl oz)
- Count: price per each
If two products aren’t in the same unit, convert first, then compare.
Conversion cheat sheet (handy on your phone)
- lb → oz: ×16
- g → oz: ÷28.3495
- kg → oz: ×35.274
- mL → fl oz: ÷29.5735
- L → fl oz: ×33.814
Where the savings hide
- Shrinkflation: packages look the same but hold less. Unit price exposes it fast.
- “Family size” ≠ cheaper: large sizes win only ~60–70% of the time in my notes.
- Multipacks: convenience tax—often worse than one big container.
- Sales math: “Buy 2 for $5” = $2.50 each (usually no combo required).
- Spoilage tax: bulk is waste if you can’t finish it—unit price + your usage beats “bigger is better.”
Fin’s Price-Book (simple system)
- Keep a tiny note (phone/Sheet): item → best unit price by store.
- Update when you see a new low.
- If this week’s price > your price-book low, wait—unless you really need it.
Quick table template (paste in and fill)
| Item | Store | Price | Size | Unit | Unit Price |
|---|---|---|---|---|---|
| Pasta sauce | A-Mart | $3.49 | 24 | oz | $0.1458/oz |
| Pasta sauce | B-Mart | $3.00 | 22 | oz | $0.1364/oz |
| Rice | Warehouse | $12.99 | 10 | lb | $0.0812/oz |
| Oats | Grocery | $4.59 | 42 | oz | $0.1093/oz |
(Values are examples—replace with your real finds.)
Unit-Price Ninja Calculator
Enter price and size; it’ll compute a comparable unit price. Add rows to compare items.
| Item | Price ($) | Size | Unit | Comparable Unit Price |
|---|
Weight compared as $/oz, volume as $/fl oz, count as $/each.
Pro-tips while you shop
- Shelf tags often show unit price—but double-check the unit type (oz vs fl oz vs each).
- House brand vs name brand: test quality with a small size first; if it passes, log its best unit price in your price-book.
- Seasonal cycles: pantry staples go on promo in predictable windows; stock a bit when the unit price hits your record low.
- Store apps: clip digital coupons only after you compare post-coupon unit price to competitors.
Fin’s take
Unit price is the flashlight. Once you compare apples-to-apples, “deals” get boring and your cart gets smarter—without feeling like homework.