Compare Two Prices Without Losing Either One

The aisle problem

Two products, two sizes, two prices, one of them on offer. Working out which is better value takes two divisions — and a normal calculator can only show you the second one. So you memorise the first result, or you write it on your hand, or you give up and buy the bigger box because bigger is usually cheaper. (It often is. Not always.)

CalcBoard opens with two independent calculator panels, free. One product per panel, both answers on screen at the same time. That is the entire feature, and it is the one that makes the comparison actually happen.

Things it makes easy

• Unit price. Price ÷ size in each panel, then read both. Our free web version does the same thing when you have a signal.
• Stacked discounts. “30% off plus 20% at checkout” is 44% off, not 50% — the discount calculator shows why.
• Splitting a bill. One panel per person when the split is not even — see the tip and bill splitter.
• Budget as you go. Keep a running total in one panel while working out individual items in another.
• Imported sizes. Ounces against grams, US against UK gallons — the converters keep those straight.

It works with no signal

Supermarkets are famously bad places to have a data connection, which is precisely where a price comparison is needed. CalcBoard is a native app with everything on-device: no loading spinner, no ads waiting to download, nothing that stops working in the back corner of a shop.

Money maths that reconciles

Most calculators — including every web calculator, ours included — compute in binary floating point, where 0.1 + 0.2 comes to 0.30000000000000004. Harmless for one sum, and quietly annoying when a long list of prices lands a cent off the receipt. CalcBoard uses exact decimal arithmetic, so it adds prices the way a till does.

Frequently Asked Questions