# Functions

Discover how **functions in Excel** help you save time. If you are new to functions in Excel, we recommend you to read our introduction to Formulas and Functions first.

1 Count and Sum: The most used functions in Excel are the functions that count and sum. You can count and sum based on one criteria or multiple criteria.

2 Logical: Learn how to use Excel's logical functions, such as IF, AND, OR and NOT.

3 Cell References: Cell references in Excel are very important. Understand the difference between relative, absolute and mixed reference, and you are on your way to success.

4 Date & Time: To enter a date, use the "/" or "-" characters. To enter a time, use the ":" (colon).

5 Text: Excel has many functions to offer when it comes to manipulating text strings.

6 Lookup & Reference: Learn all about Excel's lookup & reference functions, such as VLOOKUP, HLOOKUP, MATCH, INDEX and CHOOSE.

7 Financial: This chapter illustrates Excel's most popular financial functions.

8 Statistical: An overview of some very useful statistical functions in Excel.

9 Round: This chapter illustrates three functions to round numbers in Excel. ROUND, ROUNDUP and ROUNDDOWN.

10 Formula Errors: This chapter teaches you how to deal with some common formula errors.

11 Array Formulas: This chapter helps you understand array formulas in Excel. Single cell array formulas perform multiple calculations in one cell.