Guides
Plain-language guides that explain the ideas behind our tools: how the numbers are worked out, what the common mistakes are, and what to do with the result.
- How Loan Payments Are Calculated, With ExamplesThe formula, the interest and principal split, and what changes the cost. 4 min read.
- BMI Explained: Categories, Limits and AlternativesWhat BMI measures, what it misses and how to use it sensibly. 3 min read.
- How to Compress Images for Your WebsiteResize, pick a format and set quality, in the right order. 3 min read.
- UTM Parameters Explained: Track Every CampaignWhat each label means and how to name them for clean reports. 3 min read.
- robots.txt and Meta Tags: A Practical SEO GuideCrawling, indexing and display: what each control does. 4 min read.
- Cups to Grams: A Baking Conversion GuideWhy cups do not convert with one number, with a chart of 13 ingredients. 3 min read.
How we write our guides
Each guide starts from a question people actually ask, explains the method step by step, and uses worked examples that are calculated by code, not typed from memory. We link to the primary sources we rely on, such as standards bodies, official documentation and published research, so you can check the details yourself.
Guides are updated when a formula, a standard or a search-engine rule changes. If you spot a mistake, please tell us and we will fix it. Read more about how we test our tools.