A ratio is a fraction wearing different clothes
16:9 and 16/9 carry the same information, and simplifying works identically — divide both sides by their greatest common factor. What differs is what they describe: a fraction is usually a part of a whole, while a ratio compares two separate quantities. 3:1 means one is three times the other, and that is three quarters versus one quarter of the combined total, not three quarters versus one.
That distinction is where mixing instructions go wrong. 'Dilute 1:4' means one part concentrate to four parts water — five parts in total, not four.
Scaling and splitting
Solving A:B = C:? is the recipe question: this dish serves four and I am cooking for six, so what happens to every ingredient. Find the scale factor by dividing, then apply it. Screen dimensions work the same way — 1920 wide at 16:9 means 1080 tall.
Splitting a total is the money question: divide £1,000 in the ratio 3:2 and you add the parts first to get five shares, making them £600 and £400.
Frequently asked questions
Can I use decimals in a ratio?
Yes. Decimal parts are scaled up to whole numbers before simplifying, so 2.5:5 becomes 1:2, which is how ratios are normally written.
Is anything uploaded?
No. Nothing you type is sent to a server.
Something wrong with this tool, or an idea for it? Tell us