Go: How to Convert Float to Int with Example Code

In Go, convert a float to an int by using simple type conversion like int(yourFloat), which drops the decimal part and keeps the integer portion.

Examples

Input3.14

Output3

Input-7.99

Output-7

Input0.0

Output0

How to Think About It

To convert a float to an int in Go, think of it as taking the number and removing everything after the decimal point. You do this by telling Go to treat the float as an int using int() conversion, which simply cuts off the decimal part without rounding.

Algorithm

1

Get the float value you want to convert.

2

Use the <code>int()</code> conversion to change the float to an int.

3

Return or use the resulting integer value.

Code

go

package main

import "fmt"

func main() {
    var f float64 = 3.99
    i := int(f)
    fmt.Println(i) // Output: 3
}

Output

3

Dry Run

Let's trace converting 3.99 to int through the code

1

Start with float

f = 3.99

2

Convert float to int

i = int(f) => i = 3

3

Print result

Output: 3

Step	Value of f	Value of i	Output
1	3.99	-	-
2	3.99	3	-
3	3.99	3	3

Why This Works

Step 1: Type Conversion

Using int() tells Go to convert the float value to an integer type.

Step 2: Decimal Truncation

The conversion drops the decimal part without rounding, so 3.99 becomes 3.

Step 3: Result Usage

The resulting integer can be used wherever an int is needed, like printing or calculations.

Alternative Approaches

Using math.Floor for rounding down

go

package main

import (
    "fmt"
    "math"
)

func main() {
    f := 3.99
    i := int(math.Floor(f))
    fmt.Println(i) // Output: 3
}

This method explicitly rounds down before converting, useful if you want to be clear about rounding behavior.

Using math.Round for nearest integer

go

package main

import (
    "fmt"
    "math"
)

func main() {
    f := 3.5
    i := int(math.Round(f))
    fmt.Println(i) // Output: 4
}

This rounds the float to the nearest integer before converting, unlike simple truncation.

Complexity: O(1) time, O(1) space

Time Complexity

Conversion is a simple, direct operation with no loops, so it runs in constant time.

Space Complexity

No extra memory is needed beyond the variables holding the float and int values.

Which Approach is Fastest?

Simple type conversion int() is fastest; using math.Floor or math.Round adds function call overhead.

Approach	Time	Space	Best For
int() conversion	O(1)	O(1)	Fast truncation without rounding
math.Floor + int()	O(1)	O(1)	Explicit rounding down
math.Round + int()	O(1)	O(1)	Rounding to nearest integer