# $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.insert( [ { _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 on the `orders`

collection
converts the `qty`

to an integer as well as convert `price`

to a
decimal before calculating 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" : NumberDecimal("50.0000000000000") } { "_id" : 2, "item" : "pie", "totalPrice" : NumberDecimal("200.0") } { "_id" : 3, "item" : "ice cream", "totalPrice" : NumberDecimal("9.98") } { "_id" : 4, "item" : "almonds", "totalPrice" : NumberDecimal("25.00000000000000") }

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

instead.