Free online tools
Make Every Calculation Simple
Free online calculators for dates, time zones and everyday conversions. Get clear results in seconds — no sign-up required.
- Free to Use
- No Sign-Up Required
- Clear Results
Try “age”, “kg to lbs” or “time zone”.
Most used tools
The six tools visitors open most often
Days Between Dates Calculator
Calculate the number of days between two dates.
Business Days Calculator
Count business days between two dates, excluding Saturdays and Sundays.
Age Calculator
Calculate exact age in years, months, and days from a date of birth.
Time Zone Converter
Convert a time between major world time zones, with daylight saving applied.
Length Converter
Convert between metric and imperial length units.
Temperature Converter
Convert Celsius, Fahrenheit and Kelvin online.
Date & Time Tools
Open- Open
Days Between Dates Calculator
Calculate the number of days between two dates.
- Open
Business Days Calculator
Count business days between two dates, excluding Saturdays and Sundays.
- Open
Age Calculator
Calculate exact age in years, months, and days from a date of birth.
- Open
Countdown Calculator
Count the days until a target date, or the days since a past date.
- Open
Time Zone Converter
Convert a time between major world time zones, with daylight saving applied.
Unit Converters
Open- Open
Length Converter
Convert between metric and imperial length units.
- Open
Weight Converter
Convert kilograms, pounds, ounces, grams, stone and tonnes.
- Open
Temperature Converter
Convert Celsius, Fahrenheit and Kelvin online.
- Open
Area Converter
Convert square meters, square feet, acres and hectares.
- Open
Volume Converter
Convert liters, US and Imperial gallons, milliliters and cups.
- Open
Speed Converter
Convert km/h, mph, m/s and knots online.
Why Unitime
Free to Use
Every calculator and converter is free, with no trial period and no locked features.
No Sign-Up Required
There is no account and no login. Open a tool and start calculating straight away.
Clear Results
Each result states its unit and the rule behind it, and copies to your clipboard in one click.
Understand the numbers
All guides- 6 min read
How to Count the Days Between Two Dates
The arithmetic is simple, but the ambiguity is not. How to count calendar days, when to include the end date, and where leap years actually change the answer.
- 5 min read
Business Days, Weekends and Public Holidays
Why five business days is not five days, how to count working days by hand, and why public holidays make cross-border deadlines harder than they look.
- 6 min read
Time Zone Conversion: Five Mistakes That Cost a Meeting
Offsets are not fixed, dates change more often than you expect, and daylight saving does not switch everywhere on the same day. How to convert times without getting it wrong.
Frequently asked questions
Are the tools free to use?
Yes. Every calculator and converter on Unitime is free, with no account, no trial, and nothing locked behind a payment.
Do I need to sign up?
No. There is no sign-up and no login. Open a tool page and start calculating.
How do date calculators work?
They work on calendar dates in your device's time zone. Date differences count whole days, the business days tool removes Saturdays and Sundays, and age is counted in whole years, then months, then remaining days.
Is my input stored?
No. The dates, numbers, and units you type are processed in your browser and are not sent to our server. We collect limited, aggregate usage information to understand how the site is used — see the Privacy Policy for the details.
Do you support both metric and imperial units?
Yes. Length, weight, area, volume, and speed all include both systems. US and Imperial volume units are labelled separately so you always know which gallon you are using.