Frequently Asked Questions

Yes, every calculator on this site is completely free, with no sign-up or account required.

No. Every calculator runs entirely in your browser using JavaScript — nothing you type is sent to a server or saved anywhere.

Yes, every tool is designed to work on mobile, tablet, and desktop screens equally well.

Each calculator uses standard, widely accepted formulas, but results are estimates. Health calculators especially (BMI, BMR, body fat) are population-level approximations, not medical diagnoses — see our Disclaimer for details.

If your birthday hasn't occurred yet this year, simple year subtraction overstates your age by one. The Age Calculator checks the exact date, not just the year, and also correctly handles leap years and February 29 birthdays.

The Age Calculator is built specifically for a birth date. The Date Difference Calculator works for any two arbitrary dates — useful for trip planning, deadlines, or contract lengths — and includes an option to count the end date itself, which matters for things like counting nights of a hotel stay versus total calendar days.

The Percentage Calculator answers "what percent is X of Y" for any two numbers. The Fraction to Percentage tool is specifically for converting a fraction (like 3/4) into its percentage form (75%) — same underlying math, different input format.

Yes, both accept decimals. Negative numbers will calculate mathematically correctly, though most everyday use cases involve positive values.

No — both show the pure mathematical calculation based on principal, rate, and time. Real loans and investments often include fees, taxes, or insurance that will change your actual numbers, so treat these as close estimates rather than final figures.

No, it assumes a simple, no-interest monthly deposit. If your savings account earns interest, you'll likely reach your goal slightly faster than the estimate shown.

Lenders sometimes use a slightly different day-count convention or add processing fees and insurance into the monthly payment. This tool shows the standard principal-and-interest amortization formula only.

They use standard, widely-referenced formulas (WHO ranges for BMI, the Mifflin-St Jeor equation for BMR, and the U.S. Navy method for body fat), but none account for your individual health history, muscle mass, or medical conditions. Use them as a general reference point, and consult a doctor or dietitian for personal guidance.

Several competing formulas exist for each measurement (for example, Harris-Benedict vs. Mifflin-St Jeor for BMR). They're all close estimates using different assumptions, so small variations between sites are normal and expected.

No. It provides a general reference range using a long-standing formula, but healthy weight varies by frame size, muscle mass, and individual factors a formula can't see.

Small differences usually come from rounding at intermediate steps. This tool converts in a single calculation using precise standard ratios to avoid compounding rounding errors.

No — it converts volume only (cups, tablespoons, milliliters, etc.). Converting to weight (grams) depends on the specific ingredient's density, which this tool doesn't calculate.