Four free tools that show the working — the assumptions, the sources, and the number you actually asked for. Including, quite often, the number that says don't buy anything.
What clean-air delivery rate your room needs, which unit covers it, and what a year of running it costs.
"What size air purifier do I need?"Six questions that match a filter to your documented water problem — or tell you that you don't have one.
"Do I actually need a water filter?"What your bathroom really costs in money, paper, water and hours — plus the care and dignity case.
"Will a bidet pay for itself?"What a good night is worth per night, and how to tell whether the mattress is actually the problem.
"Is it time to replace my mattress?"Because most of them are shopping lists wearing a lab coat. You arrive with a question, you leave with a product — and the arithmetic in between was decorative.
We do it the other way round. The maths comes first and the recommendation has to survive it. If your room needs 450 CFM and the biggest unit we list delivers 391, we say so and tell you to buy two, instead of quietly linking the one that fits our commission better. That has actually happened, and it's on the record.
The air purifier calculator is available as an embeddable widget — one line of code, no cost, no tracking of your readers. If a version of one of the other tools would suit your audience, ask.