--- title: 3.11 Floor Division description: "Division does not always produce a whole number. In many situations, only the integer part of the quotient is required. Python provides the **floor division operator (`//`)** for this purpose. Floor division divides two numbers and returns the **largest integer…" url: "https://edcret.in/docs/python-programming/numeric-data-types-python/3-11-floor-division/" updated: "2026-07-29" category: Python Programming / Numeric Data Types --- # 3.11 Floor Division Division does not always produce a whole number. In many situations, only the integer part of the quotient is required. Python provides the **floor division operator (`//`)** for this purpose. Floor division divides two numbers and returns the **largest integer less than or equal to the actual quotient**. In other words, it rounds the result **down toward negative infinity**. Floor division is commonly used when calculating groups, pages, batches, rows, or any situation where only complete units are needed. --- ## Syntax ``` result = dividend // divisor ``` ### Components | Component | Description | | --- | --- | | `dividend` | The number to be divided. | | `//` | Floor division operator. | | `divisor` | The number that divides the dividend. | | `result` | The quotient rounded down to the nearest whole number. | --- ## Example 1: Floor Division of Two Integers **main.py** ``` a = 17 b = 5 print(a // b) ``` ### Output ``` 3 ``` ### Explanation - `17 ÷ 5` equals `3.4`. - Floor division removes the fractional part by rounding down. - Therefore, the result is `3`. --- ## Example 2: Division vs Floor Division **main.py** ``` a = 17 b = 5 print(a / b) print(a // b) ``` ### Output ``` 3.4 3 ``` ### Explanation - `/` performs normal division and returns `3.4`. - `//` performs floor division and returns `3`. - Use the operator that matches the required result. --- ## Example 3: Floor Division with Floating-Point Numbers **main.py** ``` print(17.5 // 4) ``` ### Output ``` 4.0 ``` ### Explanation - `17.5 ÷ 4` equals `4.375`. - Floor division rounds the result down to `4.0`. - Since one operand is a float, the result is also a float. --- ## Example 4: Floor Division with Negative Numbers **main.py** ``` print(-17 // 5) ``` ### Output ``` -4 ``` ### Explanation - `-17 ÷ 5` equals `-3.4`. - Floor division rounds toward negative infinity. - The largest integer less than or equal to `-3.4` is `-4`. --- ## Example 5: Both Operands are Negative **main.py** ``` print(-20 // -3) ``` ### Output ``` 6 ``` ### Explanation - `-20 ÷ -3` equals approximately `6.67`. - Floor division rounds down to `6`. - Since both numbers are negative, the result is positive. --- ## Example 6: User Input **main.py** ``` total = int(input("Enter total items: ")) group = int(input("Enter group size: ")) print(total // group) ``` ### Sample Input ``` 23 5 ``` ### Output ``` 4 ``` ### Explanation - `23 ÷ 5` equals `4.6`. - Only four complete groups can be formed. - Floor division returns `4`. --- ## Example 7: Calculating Complete Boxes **main.py** ``` apples = 56 box_capacity = 8 boxes = apples // box_capacity print(boxes) ``` ### Output ``` 7 ``` ### Explanation - Each box holds `8` apples. - `56 // 8` equals `7`. - Seven complete boxes can be filled. --- ## Example 8: Mixed Data Types **main.py** ``` print(25 // 4.0) ``` ### Output ``` 6.0 ``` ### Explanation - One operand is a floating-point number. - Therefore, Python returns a floating-point result. - The mathematical value is still rounded down. --- ## Example 9: Exact Division **main.py** ``` print(20 // 4) ``` ### Output ``` 5 ``` ### Explanation - `20` is exactly divisible by `4`. - No rounding is required. - The result is `5`. --- ## Example 10: Checking the Return Type **main.py** ``` print(type(20 // 4)) print(type(20.0 // 4)) ``` ### Output ``` ``` ### Explanation - When both operands are integers, the result is an integer. - If either operand is a floating-point number, the result is a float. --- # Common Mistakes ### 1. Confusing `/` with `//` **Incorrect** ``` print(15 // 4) ``` ### Incorrect Expectation ``` 3.75 ``` ### Actual Output ``` 3 ``` **Reason** `//` performs floor division, not normal division. **Correct** ``` print(15 / 4) ``` --- ### 2. Expecting Negative Results to Round Toward Zero **Incorrect** ``` print(-15 // 4) ``` ### Incorrect Expectation ``` -3 ``` ### Actual Output ``` -4 ``` **Reason** Floor division always rounds toward negative infinity, not toward zero. --- ### 3. Dividing by Zero **Incorrect** ``` print(10 // 0) ``` ### Output ``` ZeroDivisionError: integer division or modulo by zero ``` **Reason** Division by zero is not allowed. --- ### 4. Assuming the Original Variable Changes **Incorrect** ``` number = 19 number // 4 print(number) ``` ### Output ``` 19 ``` **Reason** The result of floor division is returned as a new value. The original variable remains unchanged. **Correct** ``` number = number // 4 print(number) ``` --- # Best Practices - Use `//` when only complete units are needed. - Remember that floor division rounds toward negative infinity. - Use `/` when the fractional part of the result is important. - Check for zero before performing floor division. - Store the result if it will be used later in the program. --- # Key Points to Remember - `//` is the floor division operator in Python. - Floor division returns the quotient rounded down. - It rounds toward negative infinity, not toward zero. - When both operands are integers, the result is an integer. - If either operand is a floating-point number, the result is a float. - Floor division is useful for calculating complete groups, batches, pages, and containers. - Dividing by zero raises a `ZeroDivisionError`.