How to Format a Number with Commas and Decimals in C#

Need 1234567 to print as 1,234,567? To format a number with commas in C#, call number.ToString("N0") for whole numbers or ToString("N2") for two decimals, and pass an en-US culture so the separator doesn’t change from machine to machine.

In this tutorial, I’ll cover each case I’ve hit in production code for C# format number with commas: custom patterns, interpolation, cultures, a space separator, no separators at all, currency, negatives, big numbers and parsing back.

My sample data is a US retailer’s quarterly sales in dollars, and I ran every snippet with dotnet run on .NET 10.

Format a Number with Commas Using ToString(“N0”) and “N2”

The N format specifier adds group separators, and the digit after it sets the decimal places. Here’s the same revenue figure printed several different ways:

using System.Globalization;
CultureInfo.CurrentCulture = new CultureInfo("en-US");


int unitsSold = 1234567;           // Q3 units, all US stores
double revenue = 9876543.219;      // Q3 revenue in USD

Console.WriteLine(unitsSold.ToString("N0"));
Console.WriteLine(revenue.ToString("N2"));
Console.WriteLine(revenue.ToString("#,##0.00"));
Console.WriteLine(revenue.ToString("#,##0.##"));
Console.WriteLine($"Revenue: {revenue:N2}");
Console.WriteLine(string.Format("Units: {0:N0}", unitsSold));
Console.WriteLine(revenue.ToString("N"));

var sb = new System.Text.StringBuilder();
sb.AppendFormat("Q3 total: {0:N2} USD", revenue);
Console.WriteLine(sb.ToString());

Output:

1,234,567
9,876,543.22
9,876,543.22
9,876,543.22
Revenue: 9,876,543.22
Units: 1,234,567
9,876,543.219
Q3 total: 9,876,543.22 USD

N0 gives 1,234,567 with no decimals, and N2 rounds 9876543.219 to 9,876,543.22. The custom pattern #,##0.00 prints the same thing, while #,##0.## drops trailing zeros.

The interpolated {revenue:N2} and string.Format("{0:N0}", ...) take the exact same format strings, so pick whichever reads better in your line of code. I compare the other overloads in my guide to the ToString method in C#.

Watch the plain "N" line. It printed three decimals, 9,876,543.219, because the default comes from NumberDecimalDigits, and en-US reports 3 on .NET 10 here. Always write the precision you want.

If you only care about the decimals, not the commas, my post on C# 2 decimal places with F2 and Math.Round goes deeper into rounding.

Convert a Number to a Comma-Separated String with StringBuilder

The last lines show StringBuilder.AppendFormat, which accepts the same {0:N2} item. It’s only worth it when you’re already building a long report, as I explain in string vs StringBuilder in C#.

If you actually want to join several values with commas, like "Texas, Ohio, Utah", that’s a different job. Use string.Join, as shown in how to convert a list to a comma-separated string in C#.

Why Does the C# Thousand Separator Change by Culture?

N0 and #,##0 don’t insert a literal comma. They insert the current culture’s NumberGroupSeparator, using its group sizes. I printed the same decimal in four cultures with the separator’s Unicode code point:

using System.Globalization;

decimal sales = 1234567.89m;
string[] cultures = { "en-US", "en-IN", "de-DE", "fr-FR" };

foreach (string name in cultures)
{
    var culture = CultureInfo.GetCultureInfo(name);
    string text = sales.ToString("N2", culture);
    string sep = culture.NumberFormat.NumberGroupSeparator;
    Console.WriteLine($"{name}: {text,-16} group separator U+{(int)sep[0]:X4}");
}

Console.WriteLine($"This PC's culture: {CultureInfo.CurrentCulture.Name} -> {sales:N2}");

Output:

en-US: 1,234,567.89     group separator U+002C
en-IN: 12,34,567.89     group separator U+002C
de-DE: 1.234.567,89     group separator U+002E
fr-FR: 1 234 567,89     group separator U+202F
This PC's culture: en-IN -> 12,34,567.89

This PC is set to en-IN, so without an explicit culture it groups as 12,34,567.89, the Indian lakh style. That’s exactly the kind of surprise you’ll get on a build server, and it’s why the other snippets start with en-US.

de-DE swaps the roles, a dot for groups and a comma for decimals. fr-FR uses U+202F, a narrow no-break space, not the regular space you’d type.

The same rule applies when you read numbers back in. My post on how to convert a string to double in C# shows why parsing needs the matching culture too.

Format a Number with a Space as the Thousand Separator in C#

If you want a plain space, such as 15 750 000, clone a NumberFormatInfo and set NumberGroupSeparator yourself:

using System.Globalization;
CultureInfo.CurrentCulture = new CultureInfo("en-US");


long annualVisitors = 15750000;    // yearly store visits, nationwide
decimal revenue = 48250375.5m;

var spaced = (NumberFormatInfo)CultureInfo.InvariantCulture.NumberFormat.Clone();
spaced.NumberGroupSeparator = " ";

Console.WriteLine(annualVisitors.ToString("N0", spaced));
Console.WriteLine(revenue.ToString("N2", spaced));
Console.WriteLine(revenue.ToString("#,##0.00", spaced));
Console.WriteLine(annualVisitors.ToString("N0").Replace(",", " "));

var fr = CultureInfo.GetCultureInfo("fr-FR");
string french = annualVisitors.ToString("N0", fr);
Console.WriteLine($"{french} == \"15 750 000\"? {french == "15 750 000"}");

Output:

15 750 000
48 250 375.50
48 250 375.50
15 750 000
15 750 000 == "15 750 000"? False

The clone matters, because the invariant culture’s own NumberFormat is read-only. Both N0 and #,##0.00 pick up the space, and the decimal point stays a period.

The Replace(",", " ") trick also works for en-US output, but it breaks the moment a culture uses a comma for decimals. I’d keep string surgery like removing a character from a string in C# for text, not numbers.

The last line proves the fr-FR point: its output looks identical on screen, but it isn’t equal to a string typed with normal spaces.

Format Numbers Without Commas or Thousand Separators in C#

You’ll often need digits only, for CSV files, IDs or API payloads. These formats never add a group separator:

using System.Globalization;
CultureInfo.CurrentCulture = new CultureInfo("en-US");


int orders = 1234567;
double revenue = 9876543.2;

Console.WriteLine(orders.ToString("D"));
Console.WriteLine(orders.ToString("D10"));
Console.WriteLine(orders.ToString());
Console.WriteLine(revenue.ToString("F2"));
Console.WriteLine(revenue.ToString("0.##"));
Console.WriteLine(revenue.ToString("F2", CultureInfo.InvariantCulture));
Console.WriteLine(revenue.ToString("N0", CultureInfo.InvariantCulture));

try { Console.WriteLine(revenue.ToString("D")); }
catch (FormatException) { Console.WriteLine("\"D\" on a double throws FormatException"); }

Output:

1234567
0001234567
1234567
9876543.20
9876543.2
9876543.20
9,876,543
"D" on a double throws FormatException

D works on integers only, and D10 pads to ten digits. A double needs F2, 0.## or plain ToString(), and D throws a FormatException on it.

For machine-readable output, I pass CultureInfo.InvariantCulture so the decimal point is always a period. Note that N0 with InvariantCulture still prints 9,876,543, so it doesn’t remove commas.

For fixed-width codes with zeros in front, see how to add leading zeros to a string in C#.

Format Currency, Negative and Large Numbers with Commas

For money, I use decimal with C2, which adds the dollar sign as well as the commas. Here’s a Texas region’s monthly profit, with a loss and a zero month, plus big US numbers:

using System.Globalization;
CultureInfo.CurrentCulture = new CultureInfo("en-US");


decimal[] monthlyProfit = { 1250000.5m, -48210.75m, 0m };   // Texas region, USD

foreach (decimal p in monthlyProfit)
    Console.WriteLine($"{p,14:N2} | {p,15:C2} | {p.ToString("#,##0.00;(#,##0.00);-")}");

long usPopulation = 340_110_988;
decimal nationalDebt = 37_640_000_000_000m;
Console.WriteLine(usPopulation.ToString("N0"));
Console.WriteLine(nationalDebt.ToString("C0"));
Console.WriteLine(long.MaxValue.ToString("N0"));
Console.WriteLine(nationalDebt.ToString("$#,##0,,,,.0 T"));
Console.WriteLine(usPopulation.ToString("#,##0,, M"));

Output:

  1,250,000.50 |   $1,250,000.50 | 1,250,000.50
    -48,210.75 |     -$48,210.75 | (48,210.75)
          0.00 |           $0.00 | -
340,110,988
$37,640,000,000,000
9,223,372,036,854,775,807
$37.6 T
340 M

en-US puts the minus before the dollar sign, -$48,210.75. The three-section pattern #,##0.00;(#,##0.00);- prints accounting-style parentheses and a dash for zero.

long and decimal take the same specifiers, so long.MaxValue formats fine. Commas right before the decimal point divide by 1,000 each, which is how $#,##0,,,,.0 T shows the debt in trillions.

The C# data types guide lists each type’s range, and this is the same display code I’d put at the end of a C# compound interest program.

How Do You Parse a Number with Commas Back in C#?

Formatted text doesn’t parse back by default. Pass a NumberStyles value that allows thousands separators, plus the culture that wrote it:

using System.Globalization;
CultureInfo.CurrentCulture = new CultureInfo("en-US");


var us = CultureInfo.GetCultureInfo("en-US");

decimal total = decimal.Parse("1,234,567.89", NumberStyles.Number, us);
Console.WriteLine(total + 1);

int units = int.Parse("12,500", NumberStyles.AllowThousands, us);
Console.WriteLine(units);

bool ok = int.TryParse("12,500", out int noStyle);
Console.WriteLine($"int.TryParse without AllowThousands: {ok}");

Output:

1234568.89
12500
int.TryParse without AllowThousands: False

NumberStyles.Number includes AllowThousands and AllowDecimalPoint, so the total parses and adding 1 proves it’s a real decimal. Plain int.TryParse("12,500") returns false.

For European input such as "1.234,56", follow my full walkthrough on how to convert a number with a comma into decimal in C#.

Which C# Number Format with Commas Should You Use?

You want	Use	en-US result
Whole number with commas	N0 or #,##0	1,234,567
Commas and 2 decimals	N2 or #,##0.00	9,876,543.22
US dollars	C2 on a decimal	$1,250,000.50
Space separator	cloned NumberFormatInfo + N0	15 750 000
No separators	D, F2, 0.##	1234567
Negatives in parentheses	#,##0.00;(#,##0.00)	(48,210.75)

A few more number and string conversions I get asked about a lot:

• Convert an int to a hex string with a leading zero
• Convert a string to int and keep leading zeros

Frequently Asked Questions