Date Calculator
Find the difference between two dates or add and subtract days, weeks, months and years from any date. Instant, accurate, runs entirely in your browser — no sign-up, no tracking.
- Privacy-first — nothing leaves your device
- Handles leap years, weekends and business days
- Mobile-optimised, no sign-up needed
More date calculators
Eight purpose-built calculators for the questions a quick date math widget can't answer alone — pregnancy, fertility, age, working days and live countdowns.
Pregnancy Due Date Calculator
Estimate your baby's due date and track every week of pregnancy from your last menstrual period.
Open tool →Conception Date Calculator
Work backward from a due date or birth date to estimate the most likely conception window.
Open tool →Ovulation & Fertile Window Calculator
Predict your most fertile days and ovulation date for the next three cycles.
Open tool →Age Calculator
Calculate exact age in years, months, days, weeks, hours and seconds — plus next birthday.
Open tool →Date Difference Calculator
Find the exact gap between two dates in years, months, weeks and days.
Open tool →Date Add / Subtract Calculator
Add or subtract days, weeks, months or years from any date instantly.
Open tool →Working Days Calculator
Count business days (Mon–Fri) between two dates, ideal for project planning and contracts.
Open tool →Live Countdown Timer
A live countdown to any future date — wedding, exam, holiday, launch — updates every second.
Open tool →Tools you won't find elsewhere
Three flagship features built to solve real problems we couldn't find elegantly handled anywhere else online.
Multi-Calendar Converter Unique
Convert any date across Gregorian, Hijri (Islamic), Hebrew, Persian, Buddhist, Indian and more.
Open tool →Date Memory Vault Unique
Privately save important dates in your browser and see live countdowns whenever you visit.
Open tool →Pregnancy Week-by-Week Journey Unique
An interactive timeline of fetal development from week 1 through week 40.
Open tool →Why Date Estimator?
Most calculator websites bury the answer under ads, trackers and aggressive pop-ups. Date Estimator was built around three guarantees:
- Truly private. Every calculation happens locally in your browser. No analytics on inputs.
- Genuinely fast. Pages are pre-rendered and statically delivered, scoring 95+ on Core Web Vitals.
- Always free. No sign-up, no paywall, no email harvesting — ever.
How it works
- Pick the calculator you need from the list above.
- Enter your dates — your last period, a birthday, a deadline.
- See an instant, detailed breakdown with milestones and printable summaries.
Every formula is documented on its calculator page so you can trust the math.
What you can do with Date Estimator
Whether you're an expecting parent, an HR manager counting business days for a contract, a student figuring out exam countdowns, or a developer verifying date logic, Date Estimator gives you the answer in seconds.
Pregnancy & fertility
From a single piece of information — the first day of your last menstrual period (LMP) — our pregnancy due date calculator estimates your due date using Naegele's rule (LMP + 280 days), and adapts the formula automatically when your cycle isn't the textbook 28 days. Pair it with the conception calculator and ovulation predictor for a full reproductive timeline.
Personal milestones
The age calculator doesn't just tell you years — it gives you months, weeks, days, hours and even your zodiac sign, birthstone and the number of days until your next birthday. Use the date difference calculator to commemorate anniversaries or check how long you've known someone.
Work, school & projects
The working days calculator counts only Monday-to-Friday days and is perfect for SLAs, vacation planning, contract terms and academic deadlines. The date add/subtract tool handles things like "60 days from today" or "due 9 months before the launch" with no spreadsheet gymnastics.
Cross-calendar conversions
Our Multi-Calendar Converter turns any Gregorian date into Hijri, Hebrew, Persian (Jalali), Buddhist, Indian, Coptic, Ethiopic and more — all using accurate browser-native calendars, with no third-party servers involved.
Frequently asked questions
What is a date estimator?
Are the calculators on Date Estimator accurate?
Is Date Estimator free to use?
Do you store the dates I enter?
Can I use these results for medical or legal decisions?
Does Date Estimator work offline?
Pick a tool and get an answer in seconds.
Bookmark this page — you'll likely come back the next time someone asks how many days until something or how old someone really is.