# Formulas

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A spreadsheet formula is an equation that performs a calculation on the numbers, functions and values of one or more cells. A formula is associated with a cell or a cell range. It is accessed using the CellRange.Formula property.

## Formula Types

Formula Type | Description |
---|---|

Normal | Use the CellRange.Formula property to assign a formula to a cell or to each cell in a range. Refer to the Creating Formulas document for examples of creating formulas. |

Shared | Shared formula is created automatically when required without user intervention when you assign a formula string to an array of cells. A specified formula is associated with each cell contained within the specified cell range. Shared formulas are used internally to optimize calculations and file size. Refer to the How to: Create Shared Formulas document for more information. |

Array | An array formula is a special kind of formula used to perform calculations with arrays of cells. Use the CellRange.ArrayFormula property or ArrayFormulaCollection.Add methods to include array formulas in your worksheet. An array formula for a cell or a range is accessible via the CellRange.ArrayFormula property. To find an array formula range that includes a particular cell, use the Cell.GetArrayFormulaRange method. For more information on array formulas, see the Array Formulas document. |

## Formula Syntax

A formula is a string expression that begins with an equal (=) sign. A formula can contain the constants, operators, cell references, calls to functions, and names.

Consider the following formula, which calculates the mass of a sphere.

**=4/3 PI()(A2^3)*Density**

- “4” and “3” are
**numeric constants**. Although they are written as integers, the division operator (/) interprets them as being real numbers, i.e., 4.0 and 3.0. As a result, the calculation produces a precise result that is not rounded to an integer. - “/” is the division operator.
- “PI()” results in a call to the PI function, which returns the value of π.
- “A2” is a cell reference, which returns the value within that specific cell.
- “3” is a
**numeric constant**. - “^” is the caret
**operator**, which raises the left operand to the power of the right operand. **Parentheses**are used for grouping and changing the operator precedence.- “
*” is the asterisk (*)**operator**, which performs multiplication. - The
**Density**is a defined name within the worksheet that can represent a cell range, a function or a constant.

The formula is calculated from left to right, according to the operator precedence. To change the order of calculation you can enclose a portion of the formula in parentheses.

## Parts of a Formula

## Calculation

To recalculate all formulas in a workbook, call the IWorkbook.Calculate method. The DocumentSettings.Calculation property provides access to calculation options. Calculation results are placed in the CellRange.Value property of corresponding cells. See the Calculation Process topic for more information.

You can also calculate a formula and leave the document unchanged by using the IWorkbook.Evaluate method.

## Formula Engine

The FormulaEngine is an object that provides the capability to calculate and parse worksheet formulas. It includes a built-in formula parser, as well as the flexibility to evaluate formulas in any range of any worksheet. See the Formula Engine topic for more information.