Best, Cool New Features in the Windows 7 Calculator

You can use Windows 7 Calculator to perform simple calculations such as addition, subtraction, multiplication, and division. Windows 7 Calculator also offers the advanced capabilities of a programming, scientific, and statistical calculator.
Go to Start > Search for calc to use calculator.
If you are using XP or Vista you can download the Windows 7 calculator (Link)
Similar : Get Windows 7 Paint for XP, Vista

New Improved Features of Windows Seven Calculator

Using History to View all Calculations Done Previously

• Click the View menu, and then click History (Ctrl+H).
• Use the up, down arrows to browse through the operations done and also double click to edit them, and the results update with them.

New Programmer Mode in Windows 7 Calculator

• Click the View menu, and then click Programmer.
• Click the calculator keys to perform the calculation you want.

In Programmer mode, Calculator is precise up to 64 bits, depending on the word size that you’ve selected.

• Calculator honors operator precedence when calculating in Programmer mode.
• Programmer mode is an integer only mode. Decimal portions are discarded.

Calculate, Perform Unit Conversions

You can use Calculator to perform conversions for different units of measure.

• Click the View menu, and then click Unit conversion.
• Under Select the type of unit you want to convert, click the three lists to select the types of units you want to convert, and then, in the From box, enter the value that you want to convert.

Tip : Set Inactive Windows to Minimize Automatically

Find Difference in Days between Two Dates

You can use Calculator to calculate the difference between two dates or to add or subtract days from a specified date.

• Click the View menu, and then click Date calculation.
• Under Select the date calculation you want, click the list and select the type of calculation that you want to perform.
• Enter the information, and then click Calculate.

Calculate Fuel Economy, Lease Payments, and Mortgage Payments

You can use the Fuel economy, Vehicle lease, and Mortgage templates in Calculator .

• Click the View menu, point to Worksheets, and then click the worksheet for the calculation you want.
• Under Select the value you want to calculate, click the variable that you want to calculate.
• Enter the known values in the text boxes and then click Calculate.

Using Statistics Mode – Calculate Mean, Standard Deviation etc

When you use Statistics mode, you can enter the data that you want to calculate statistics for and then perform the calculations. When you enter the data, it’s displayed in the history area and the number of values you have entered is displayed in the calculation area.

• Click the View menu, and then click Statistics.
• Type or click your first piece of data, and then click Add to add the data to the dataset.
• Click the button for the statistical calculation you want to perform:
  

I was really excited to see so many new features in windows seven calculator.