About CalcFern

CalcFern is a one-person project. I'm Eisa Akber, a web developer, and I built this site because converting a unit usually meant three tabs and none of them showed the formula they were using.

What you get here

• Unit converters for length, weight, area, volume, temperature, speed, time, data and pressure. Every converter shows the exact factor it uses and a reference table you can check it against.
• Calculators for everyday maths and money (percentages, discounts, simple interest, salary to hourly), health estimates (BMI, BMR, calorie deficit, ideal weight, water intake) and text (word and character counts, case conversion, JSON formatting).
• Guides that explain the conversion or formula in plain English, with worked examples.

Where the numbers come from

Conversion factors are the SI definitions published by the BIPM and NIST — for example 1 inch = 25.4 mm and 1 lb = 0.45359237 kg exactly. Health calculators use published equations (WHO/CDC BMI categories, the Mifflin-St Jeor equation for BMR, the Devine/Robinson/Miller/Hamwi ideal-weight formulas) and each tool page cites its sources and states its limits. They are screening aids and rules of thumb, not medical or financial advice — see the disclaimer.

How the site is made

The calculators and their reference tables are generated by code I wrote and test against known values; the explanations, guides and examples are written by me. Nothing you type into a tool is sent to a server — every calculation runs in your browser. Details are in the editorial policy.

Mistakes and requests

If a result looks wrong, or you need a converter that isn't here, tell me. Corrections are made on the page and dated. The site is free to use; it may show advertising to cover hosting, and ads never influence results.