# $toInt (aggregation)

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## Definition

`$toInt`

*New in version 4.0*.Converts a value to an integer. If the value cannot be converted to an integer,

`$toInt`

errors. If the value is null or missing,`$toInt`

returns null.`$toInt`

has the following syntax:{ $toInt: <expression> } The

`$toInt`

takes any valid expression.The

`$toInt`

is a shorthand for the following`$convert`

expression:{ $convert: { input: <expression>, to: "int" } } TipSee also:

## Behavior

The following table lists the input types that can be converted to an integer:

Input Type | Behavior |
---|---|

Boolean | Returns `0` for `false` .Returns `1` for `true` . |

Double | Returns truncated value. The truncated double value must fall within the minimum and maximum value for an integer. You cannot convert a double value whose truncated value is less than the minimum integer value or is greater than the maximum integer value. |

Decimal | Returns truncated value. The truncated decimal value must fall within the minimum and maximum value for an integer. You cannot convert a decimal value whose truncated value is less than the minimum integer value or is greater than the maximum integer value. |

Integer | No-op. Returns the integer value. |

Long | Returns the long value as an integer. The long value must fall within the minimum and maximum value for an integer. You cannot convert a long value that is less than the minimum integer value or is greater than the maximum integer value. |

String | Returns the numerical value of the string as an integer. The string value must be a base You cannot convert a string value of a float or decimal or
non-base |

The following table lists some conversion to integer examples:

Example | Results |
---|---|

`$toInt: true` | 1 |

`$toInt: false` | 0 |

`$toInt: 1.99999` | 1 |

`$toInt: NumberDecimal("5.5000")` | 5 |

`$toInt: NumberDecimal("9223372036000.000")` | Error |

`$toInt: NumberLong("5000")` | 5000 |

`$toInt: NumberLong("922337203600")` | Error |

`$toInt: "-2"` | -2 |

`$toInt: "2.5"` | Error |

`$toInt: null` | null |

## Example

Create a collection `orders`

with the following documents:

db.orders.insertMany( [ { _id: 1, item: "apple", qty: "5", price: 10 }, { _id: 2, item: "pie", qty: "10", price: NumberDecimal("20.0") }, { _id: 3, item: "ice cream", qty: "2", price: "4.99" }, { _id: 4, item: "almonds" , qty: "5", price: 5 } ] )

The following aggregation operation:

- converts
`qty`

to an integer, - converts
`price`

to a decimal, - calculates the total price:

// Define stage to add convertedPrice and convertedQty fields with the converted price and qty values priceQtyConversionStage = { $addFields: { convertedPrice: { $toDecimal: "$price" }, convertedQty: { $toInt: "$qty" }, } }; // Define stage to calculate total price by multiplying convertedPrice and convertedQty fields totalPriceCalculationStage = { $project: { item: 1, totalPrice: { $multiply: [ "$convertedPrice", "$convertedQty" ] } } }; db.orders.aggregate( [ priceQtyConversionStage, totalPriceCalculationStage ] )

The operation returns the following documents:

{ _id: 1, item: 'apple', totalPrice: Decimal128("50") }, { _id: 2, item: 'pie', totalPrice: Decimal128("200.0") }, { _id: 3, item: 'ice cream', totalPrice: Decimal128("9.98") }, { _id: 4, item: 'almonds', totalPrice: Decimal128("25") }

If the conversion operation encounters an error, the aggregation
operation stops and throws an error. To override this behavior, use
`$convert`

instead.