How to Round a Double Value to an Integer Value in C#

Muhammad Maisam Abbas Feb 02, 2024

Rounding double values to integers is a common operation in programming, especially when dealing with mathematical calculations or financial applications. In C#, there are several methods available to achieve this task, each with its own characteristics and use cases.

In this guide, we’ll explore different approaches to round a double value to an integer in C#.

Round Up a Double Value to an Integer Value With the `Math.Ceiling()` Function in C#

The `Math.Ceiling()` function in C# returns the smallest integral value greater than or equal to the specified double-precision floating-point number. In simpler terms, it rounds up the given value to the nearest integer.

The method takes a `double` parameter and returns a `double`. To obtain an integer result, you can cast the result to an integer using `(int)`.

Here’s a basic example demonstrating how to use `Math.Ceiling()` to round up a `double` value:

``````using System;

class Program {
static void Main() {
double doubleValue = 10.75;
int roundedValue = (int)Math.Ceiling(doubleValue);

Console.WriteLine(\$"Original value: {doubleValue}");
Console.WriteLine(\$"Rounded up value: {roundedValue}");
}
}
``````

Output:

``````Original value: 10.75
Rounded up value: 11
``````

In this example, the `Math.Ceiling()` function is applied to the `doubleValue`, and the result is cast to an integer. The output will display the original value and the rounded-up value.

Let’s consider a practical scenario where rounding up is commonly used - calculating the total cost of items in a shopping cart.

Assume you have a list of product prices stored as `double` values, and you want to calculate the total cost:

``````using System;
using System.Linq;

class Program {
static void Main() {
double[] productPrices = { 12.99, 8.75, 24.50, 15.30 };

double totalCost = productPrices.Sum();
int roundedTotalCost = (int)Math.Ceiling(totalCost);

Console.WriteLine(\$"Total cost before rounding is {totalCost}");
Console.WriteLine(\$"Rounded total cost is {roundedTotalCost}");
}
}
``````

Output:

``````Total cost before rounding is 61.54
Rounded total cost is 62
``````

In this example, the `Sum()` method is used to calculate the total cost of the products, and `Math.Ceiling()` is applied to round up the total cost to the nearest integer.

The results are then displayed, showing the total cost before and after rounding.

Round a Double Value to an Integer Value With `Math.Round()` in C#

The `Math.Round` method in C# is part of the `System` namespace and provides a flexible way to round a floating-point number to the nearest integral value. By default, `Math.Round` uses the “round half to even” strategy, which means it rounds to the nearest even number in case of a tie (midpoint).

However, for our purposes, we’ll focus on rounding to the nearest integer.

Here is the basic syntax:

``````Math.Round(double value);
``````

This version of `Math.Round()` takes a `double` value and rounds it to the nearest integer using the default rounding strategy, bankers’ rounding.

``````using System;

class Program {
static void Main() {
double doubleValue = 10.75;
int roundedValue = (int)Math.Round(doubleValue);

Console.WriteLine(\$"Original value: {doubleValue}");
Console.WriteLine(\$"Rounded value: {roundedValue}");
}
}
``````

Output:

``````Original value: 10.75
Rounded value: 11
``````

In this example, `Math.Round` is applied to the `doubleValue`, and the result is cast to an integer. The output will display the original value and the rounded value.

Custom Rounding Strategies With `Math.Round`

Additionally, `Math.Round()` has other overloaded versions that allow you to customize the rounding behavior. Here is an example of a more complex syntax:

``````Math.Round(double value, int decimals, MidpointRounding mode);
``````

Where:

• `value`: The number to be rounded.
• `decimals`: The number of decimal places to round to.
• `mode`: An enumeration of type `MidpointRounding` that specifies how to round the value in case of a tie (midpoint).

You can customize the rounding behavior by using this overloaded version of `Math.Round`. For example, you can specify the number of decimal places to round to or use the `MidpointRounding` enumeration to control the rounding strategy.

``````using System;

class Program {
static void Main() {
double doubleValue = 10.75;

// Round to 1 decimal place
double roundedToOneDecimal = Math.Round(doubleValue, 1);

int roundedAwayFromZero = (int)Math.Round(doubleValue, MidpointRounding.AwayFromZero);

Console.WriteLine(\$"Original value: {doubleValue}");
Console.WriteLine(\$"Rounded to 1 decimal place: {roundedToOneDecimal}");
Console.WriteLine(\$"Rounded away from zero: {roundedAwayFromZero}");
}
}
``````

Output:

``````Original value: 10.75
Rounded to 1 decimal place: 10.8
Rounded away from zero: 11
``````

In this example, we round `doubleValue` to one decimal place and also demonstrate rounding away from zero using `MidpointRounding.AwayFromZero`.

Dealing With Ties and `MidpointRounding`

When dealing with midpoint values (those exactly halfway between two integers), the default behavior of `Math.Round` is to round to the nearest even number. However, you can customize this behavior with the `MidpointRounding` enumeration.

``````using System;

class Program {
static void Main() {
double midpointValue = 0.5;

// Default behavior (round to the nearest even number)
int roundedDefault = (int)Math.Round(midpointValue);

int roundedAwayFromZero = (int)Math.Round(midpointValue, MidpointRounding.AwayFromZero);

Console.WriteLine(\$"Midpoint value: {midpointValue}");
Console.WriteLine(\$"Rounded (default): {roundedDefault}");
Console.WriteLine(\$"Rounded away from zero: {roundedAwayFromZero}");
}
}
``````

Output:

``````Midpoint value: 0.5
Rounded (default): 0
Rounded away from zero: 1
``````

In this example, we demonstrate the default behavior and rounding away from zero for a midpoint value.

Round a Double Value to an Integer in C# Using `Math.Floor`

The `Math.Floor` method in C# is part of the `System` namespace and is designed to return the largest integer less than or equal to the specified number. When applied to a positive `double` value, `Math.Floor` effectively removes the fractional part, rounding down to the nearest whole number.

Let’s have a basic example of using `Math.Floor` to round a `double` value down to the nearest integer:

``````using System;

class Program {
static void Main() {
double doubleValue = 10.75;
int roundedValue = (int)Math.Floor(doubleValue);

Console.WriteLine(\$"Original value: {doubleValue}");
Console.WriteLine(\$"Rounded down value: {roundedValue}");
}
}
``````

Output:

``````Original value: 10.75
Rounded down value: 10
``````

In this example, `Math.Floor` is applied to the `doubleValue`, and the result is cast to an integer. The output will display the original value and the rounded-down value.

Now, consider a scenario where you have a quantity of items represented as a `double` value, and you want to round it down to the nearest whole number:

``````using System;

class Program {
static void Main() {
double quantity = 7.8;
int roundedQuantity = (int)Math.Floor(quantity);

Console.WriteLine(\$"Original quantity: {quantity}");
Console.WriteLine(\$"Rounded down quantity: {roundedQuantity}");
}
}
``````

Output:

``````Original quantity: 7.8
Rounded down quantity: 7
``````

Here, `Math.Floor` is used to round down the `quantity` to the nearest integer. The results are then displayed, showing the original quantity and the rounded-down quantity.

Round Up a Double Value to an Integer in C# With `Math.Truncate` and `Math.Sign`

The `Math.Truncate` function in C# returns the integral part of a specified double-precision floating-point number. This effectively removes the fractional part of the number, leaving only the integer component.

On the other hand, `Math.Sign` returns an integer that indicates the sign of a double-precision floating-point number.

By combining these two functions, we can round a positive `double` value up to the nearest integer. The `Math.Truncate` function removes the decimal part, and the `Math.Sign` ensures that we round up rather than down for positive numbers.

Here’s a simple example demonstrating how to use `Math.Truncate` and `Math.Sign` to round up a `double` value:

``````using System;

class Program {
static void Main() {
double doubleValue = 10.75;
int roundedValue = (int)(Math.Truncate(doubleValue) + Math.Sign(doubleValue));

Console.WriteLine(\$"Original value: {doubleValue}");
Console.WriteLine(\$"Rounded up value: {roundedValue}");
}
}
``````

Output:

``````Original value: 10.75
Rounded up value: 11
``````

In this example, `Math.Truncate` is applied to remove the decimal part of `doubleValue`, and `Math.Sign` ensures that we round up for positive numbers. The result is cast to an integer to obtain the rounded-up value.

The output will display the original value and the rounded-up value.

Consider a scenario where you have a quantity of items represented as a `double` value, and you want to round it up to the nearest whole number:

``````using System;

class Program {
static void Main() {
double quantity = 7.3;
int roundedQuantity = (int)(Math.Truncate(quantity) + Math.Sign(quantity));

Console.WriteLine(\$"Original quantity: {quantity}");
Console.WriteLine(\$"Rounded up quantity: {roundedQuantity}");
}
}
``````

Output:

``````Original quantity: 7.3
Rounded up quantity: 8
``````

In this example, `Math.Truncate` is used to remove the decimal part of the `quantity`, and `Math.Sign` ensures that the rounding is done towards positive infinity.

The results are then displayed, showing the original quantity and the rounded-up quantity.

Conclusion

We have discussed the different methods for rounding double values to integers in C#. Whether utilizing the straightforward `Math.Ceiling()` for rounding up, the versatile `Math.Round()` for customizable rounding strategies, the precise `Math.Floor()` for rounding down, or the combination of `Math.Truncate()` and `Math.Sign()` for rounding up positive values, you now have a range of tools at your disposal.

The choice of method depends on the specific needs of the application, offering flexibility to handle diverse scenarios such as calculating costs in a shopping cart or dealing with quantities of items.

Maisam is a highly skilled and motivated Data Scientist. He has over 4 years of experience with Python programming language. He loves solving complex problems and sharing his results on the internet.