Date & Time Tools
Date Calculator
Add or subtract years, months, weeks and days from a calendar date.
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Date & Time Tools
Add or subtract calendar time, measure the span between two dates, and estimate a pregnancy due date.
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Date & Time Tools
Date Difference Calculator
Calculate the difference between two dates in years, months, weeks, days and business days (Mon–Fri). For a project, leave or any date span — not age from a date of birth.
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Date & Time Tools
Pregnancy Due Date Calculator
Estimate a due date, conception date and gestational age from LMP, a known due date or conception using Naegele’s 280-day rule.
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Related guides
- How to Calculate a Pregnancy Due DateNaegele’s rule is a 40-week calendar from LMP. Ultrasound and cycle length can move the date. This page will not replace a clinician.
- How to Calculate Daily CaloriesMaintenance calories are BMR times activity. A 500 kcal gap is a common planning figure — not a guarantee of 0.5 kg a week.
- How to Calculate Discount and Sale Price“20% off” means you pay 80%. Reconstructing the original from a sale tag is a different formula.
- How to Calculate PercentagePercent means “per hundred”. Most day-to-day questions collapse into three formulas — and one division-by-zero trap.
- How to Calculate AgeAge is a calendar difference, not “days ÷ 365”. Here is the method this site uses, including leap days.
- How to Calculate BMIBody mass index is a height-and-weight ratio, not a diagnosis. Here is the formula this calculator uses.