Money & Finance
How VAT Works: Adding and Removing It, and Sales Tax Compared
To remove 20% VAT you divide by 1.2, not subtract 20%. Follow the formulas, a supply-chain example, and a comparison with sales tax.
Reeliy Editorial Team
Reeliy Editorial Team is the name every tool, guide and article on Reeliy is published under. Every tool is tested against worked examples, the standard formula or a published reference where one exists, and other calculators. Confirmed errors are corrected promptly.
Articles do not all go through the same checks, so here is what applies to which. The articles dated 19 October 2026 are the launch set. They were published together under the operator's overall plan for the site. Each was checked when it was written and was covered by the site-wide audits, but none had a separate second check of its own before it went live.
Articles scheduled from 25 October 2026 follow a plan the site's operator approved, and a separate second check re-verifies every number and claim in each one before it is scheduled. The operator can pause, change or remove any article. No individual is named here, no professional credentials are claimed, and the tools have not been audited by an outside specialist. The full standards are in the Editorial Policy; to report a mistake or suggest a tool, get in touch.
Featured articles
Math & Statistics
Percent Error Formula: How to Calculate It With Examples
Percent error tells you how far a measurement is from the accepted value, relative to that value. Here is the formula, two worked examples and the usual traps.
Money & Finance
APR vs APY: What the Two Rates Really Tell You
APR and APY are two ways to quote the same rate. One ignores compounding and one includes it, and mixing them up can make a worse deal look better.
Money & Finance
The Compound Interest Formula, Step by Step
Compound interest is interest that earns interest. Here is the formula, a full worked example, and how to rearrange it to find the interest, the time or the rate.
Money & Finance
Does Compounding Frequency Matter? Daily vs Monthly vs Yearly
Moving from yearly to monthly compounding adds a visible amount; moving from daily to continuous adds under a dollar. The numbers show where the gains run out.
Money & Finance
Simple vs Compound Interest: How the Gap Grows
Simple interest grows in a straight line and compound interest curves upward. A side-by-side example shows how small the gap is at first and how large it becomes.
Time & Dates
Daylight Saving Time: Why Some Days Have 23 or 25 Hours
When clocks change, a local day is no longer 24 hours. Learn what shifts, how it alters durations and meeting times, and how to calculate safely.
Time & Dates
Leap Year Rules Explained: Why 1900 Was Not but 2000 Was
Every fourth year is a leap year, except when it is not. Learn the full three-part rule, the reason behind it and a formula for counting leap years.
Health & Fitness
Sleep Cycles and Bedtimes: Working Out When to Sleep
Count back from your wake-up time in blocks of about 90 minutes to find a sensible bedtime. Here is the arithmetic, a quick-reference table and what the method cannot promise.
Health & Fitness
BMI for Children and Teens: Why Percentiles Replace Cutoffs
A child's BMI is calculated like an adult's, but it is judged against other children of the same age and sex. Here is how percentiles work and what the bands mean.
Health & Fitness
Healthy Weight Range for Your Height: How It Is Calculated
A healthy weight range is a BMI band turned back into kilograms. Here is the arithmetic, a table for common heights, and why a range beats a single ideal number.
Health & Fitness
How to Calculate BMI by Hand in Metric and Imperial Units
BMI is one division and one squared number. Here is the metric and imperial method, the common unit slips, and how to run the formula backwards to find a target weight.