PostgreSQL 18 reference · Math Functions

PostgreSQL TRUNC() Function

Truncate a number toward zero, optionally keeping some decimal places: trunc(2.789, 2) is 2.78.

PostgreSQL 18

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Syntax

trunc(x)  |  trunc(x numeric, places)

Parameter	Description
`x`	A number (`integer`, `numeric` or `double precision`).
`places` optional	Decimal places to keep. Default: `0`

A number.

Toward zero

SELECT trunc(2.7) AS a, trunc(-2.7) AS b, trunc(2.789, 2) AS c;

Output

 a | b  |  c
---+----+------
 2 | -2 | 2.78
(1 row)

Run this on your computer — see “Get Started” for setup.

trunc() vs floor()

SELECT trunc(-2.7) AS trunc, floor(-2.7) AS floor;

Output

 trunc | floor
-------+-------
    -2 |    -3
(1 row)

Run this on your computer — see “Get Started” for setup.

ROUND() · Round a number to a given number of decimal places (0 by default). numeric rounds halves away from zero.
FLOOR() · Round a number down to the nearest integer: floor(2.9) is 2 and floor(-2.1) is -3.
SQL Aggregate Functions · tutorial