Calculator Methodology

Each calculator on CalculatorGo uses well-documented formulas and methods. This page provides a summary of the methodology used for each category.

Date & Time Calculators

Age and date calculators use standard date arithmetic, correctly accounting for varying month lengths and leap years. The age calculation borrows days from the previous month and months from the year as needed.

Health Calculators

BMR Calculator

Uses the Mifflin-St Jeor equation (1990), considered one of the most accurate predictive equations for Basal Metabolic Rate in healthy individuals. Activity multipliers are based on the Harris-Benedict activity factor scale.

Pregnancy & Women's Health

Due Date (EDD) / Pregnancy

Uses Naegele's Rule: EDD = LMP + 280 days. Assumes a 28-day cycle with ovulation on day 14. Referenced by ACOG, NHS and WHO.

Ovulation & Period

Ovulation is estimated at 14 days before the next period (luteal phase). The fertile window is estimated as 5 days before ovulation through 1 day after. Period predictions are based on average cycle length.

Education

Attendance Calculator

Uses the standard attendance formula: Attendance % = (Classes Attended ÷ Total Classes) × 100. The "classes needed" formula solves for the number of additional consecutive classes required to reach a target percentage.

Finance

Stock Average Calculator

Uses the weighted average formula: Average Price = Total Invested ÷ Total Shares. Each purchase is weighted by quantity.

Math

Average Calculator

Calculates arithmetic mean (sum ÷ count), median (middle value of sorted data), minimum, maximum and range.

Fun & Entertainment

Love and FLAMES calculators use name-based algorithms for entertainment only. Numerology uses the Pythagorean letter-to-number system. None of these have scientific validity.