About this site

Hi, I'm Michał Białas — Michalbs87 online — an IT enthusiast from Poland. Hardware, software, you name it: I build and fix computers for myself and my family, write code and like tools that do one job well. I use AI a lot, for many different tasks — it simply makes life easier.

I built this site myself, and I maintain everything on it: the calculator, the guides and the translations. "Myself" doesn't mean I didn't use AI — but it's not a case of writing a prompt and forgetting about it. It's a process, and a long one: many mistakes, many fixes. AI is more like a helpful coworker and a pretty smart tool, but it needs guidance — sometimes a lot of it.

It started with a situation most shoppers know. Two packs on the shelf: one says 500 g, the other 18 oz. One is on sale, the other is bigger. The shelf tags — when they show a unit price at all — don't use the same unit, and a product you have bought for years may have quietly shrunk from 10 oz to 9 oz while the price stayed the same.

Working that out on a phone calculator in the aisle takes longer than it should, and most online calculators are buried under ads and pop-ups. So I built one that converts the units, does the division and shows the answer as a bar you can read at a glance — in the time it takes to type two prices.

• It is a free calculator. No account, no sign-up, no paywall.
• It compares up to four products in any mix of US and metric units, including multipacks and count items such as diapers, sheets or laundry loads.
• It does not track or collect store prices. Every number in a comparison comes from you, and the calculation runs in your browser.
• It does not sell anything and is not affiliated with any store, brand or price comparison service.
• It is paid for by ads (Google AdSense). Ads are shown below the results — never inside the calculator.

Every size is converted to one base unit per kind of measure: ounces for weight, US fluid ounces for volume and items for counts. The price per unit is then simply price ÷ (size × number of items in the pack), and the result is shown in whichever unit you pick — per kg, per 100 g, per lb, per oz, per liter and so on.

Numbers are rounded only for display: two decimals for prices of a cent or more, three or four for smaller amounts, so a tiny per-sheet price never shows as zero. The winner and the percentage are always worked out from the unrounded values. Differences under 1% are reported as "nearly the same", and a weight is never compared with a volume — ounces and fluid ounces measure different things.

Each guide answers one real shopping question and shows the math, so you can check every step yourself. Prices in the examples are clearly hypothetical illustrations, not current market data, and every worked example is re-checked with the calculator before it is published. Nothing on the site is sponsored.

When something changes, or a reader points out a mistake, the page is corrected and its "Last updated" date changes. Spotted an error? Please tell me.