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Add or Subtract Days from Any Date — Free Online Calculator

You know the start date. You need to know what date falls 30, 60, or 90 days later. Or maybe you need to work backwards from a deadline. Either way, counting days on a calendar by hand is the kind of task that sounds simple and wastes 10 minutes you don’t have.

This calculator does it in one click. Pick your start date, choose to add or subtract, enter the number of days — and you get the result date immediately.

How to Use the Add / Subtract Days Calculator

It’s a 4-step tool. No guesswork needed.

Step 1 — Enter a Start Date Type in the date you’re starting from or click the calendar icon to pick it. The calculator defaults to today’s date, so if you’re calculating from now, you don’t need to change anything.

Step 2 — Choose Your Operation Select Add (+) if you want a future date. Select Subtract (−) if you want a past date. That’s it — there’s no complicated toggle or mode-switching.

Step 3 — Enter the Amount Type in the number. 7 for a week. 30 for a month-ish. 365 for a year. Whatever number applies to your situation.

Step 4 — Choose a Unit Pick Days, Weeks, or Months from the Unit dropdown. Then hit Calculate Result Date and your answer appears instantly.

What Can You Use This Calculator For?

More than you’d expect. Here are the situations people actually use this tool for:

Project Deadlines

Your client gives you a 45-day turnaround. Add 45 days to the contract start date and you know exactly when you need to deliver — no mental math, no calendar-flipping.

Medical & Health Tracking

Doctors often give instructions in days: “come back in 14 days,” “take this for 10 days,” “follow up in 6 weeks.” This calculator handles all of those units, so you don’t have to guess which Tuesday that lands on.

Legal & Contract Periods

Contracts specify notice periods, response windows, and expiration dates in days. A 90-day termination clause, a 30-day right of first refusal, a 60-day option period — use this tool to pin down the exact end date every time.

Return & Warranty Windows

Most products come with a 14, 30, or 90-day return window. Add that window to your purchase date and you know your last day to act before losing the option.

Pregnancy & Due Date Tracking

A standard pregnancy runs about 280 days from the first day of the last menstrual period. Add 280 days to get an estimated due date, or subtract to track how far along you are.

Visa & Travel Deadlines

Many tourist visas are issued for 30, 60, or 90 days. Add that to your entry date to know exactly when you need to leave or renew — before the immigration office reminds you the hard way.

Subscription & Trial Periods

Free trials that run 7, 14, or 30 days. Add that to your sign-up date and you know when you’ll be charged — and when to cancel if you’re not interested.

Loan & Finance Due Dates

Loan terms are often quoted in days or months. Add the term length to the start date to find the maturity date, or track when your next payment falls.

Fitness & Training Plans

12-week program starting Monday? Add 84 days to find your end date. Training for a race 90 days out? Subtract 90 days from race day to set your start date.

Event Planning

Planning a wedding, birthday, or launch? Work backwards. Subtract 60 days for invitations, 30 days for final headcount, 7 days for last-minute prep. Knowing those exact dates makes planning far less chaotic.

Why Counting Days by Hand Goes Wrong

A calendar sounds like a simple tool. But the moment you cross a month boundary — especially near February, or a leap year — manual counting falls apart quickly.

February has 28 days most years. 29 in a leap year. April, June, September, and November have 30. Everyone else has 31. If you’re counting forward 45 days from January 20, you cross two months with different lengths. People regularly land on the wrong date by 1 or 2 days.

The stakes matter. Miss a return window by a day and you’re stuck with the product. Miss a visa deadline by a day and you’re at the immigration office explaining yourself. Miss a contract notice period by a day and you may be locked into another year.

This calculator accounts for all of it automatically — varying month lengths, leap years, and date rollovers — so your result is accurate every time.

Add vs. Subtract — When to Use Each

Use Add (+) when:

• You want to find a future date
• You have a start date and a time window (e.g. “90 days from today”)
• You’re calculating when a deadline, expiration, or event falls
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Use Subtract (−) when:

• You want to find a past date
• You have an end date and need to count backwards (e.g. “what date was 30 days before March 15?”)
• You’re working backwards from a deadline to find your start point

Both operations use the same tool — just switch the dropdown.

Understanding the Units

Days — The most precise option. Use this when your window is specified in exact days: 14-day trial, 30-day return, 90-day visa.

Weeks — Useful for schedules measured in weeks: training programs, school terms, project phases. 1 week = 7 days, always.

Months — Used for longer planning horizons: 3-month contracts, 6-month subscriptions, 12-month warranties. Note that months vary in length (28 to 31 days), so the calculator uses the actual calendar month rather than assuming 30 days.

Common Date Calculations People Search For

These are the scenarios this tool handles in seconds: