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C numeric limits interface - cppreference.com

See also std::numeric_limits interface.

Characteristics of integer types

Characteristics of core language integer types

Defined in header <climits>

BOOL_WIDTH

(C++26)

 bit width of bool
(macro constant) [edit]

CHAR_BIT

 bit width of byte
(macro constant) [edit]

MB_LEN_MAX

 maximum number of bytes in a multibyte character
(macro constant) [edit]

CHAR_WIDTH

(C++26)

 bit width of char
(macro constant) [edit]

CHAR_MIN

 minimum value of char
(macro constant) [edit]

CHAR_MAX

 maximum value of char
(macro constant) [edit]

SCHAR_WIDTHSHRT_WIDTHINT_WIDTHLONG_WIDTHLLONG_WIDTH

(C++26)(C++26)(C++26)(C++26)(C++26)

 bit width of signed char, short, int, long, and long long respectively
(macro constant) [edit]

SCHAR_MINSHRT_MININT_MINLONG_MINLLONG_MIN

(C++11)

 minimum value of signed char, short, int, long and long long respectively
(macro constant) [edit]

SCHAR_MAXSHRT_MAXINT_MAXLONG_MAXLLONG_MAX

(C++11)

 maximum value of signed char, short, int, long and long long respectively
(macro constant) [edit]

UCHAR_WIDTHUSHRT_WIDTHUINT_WIDTHULONG_WIDTHULLONG_WIDTH

(C++26)(C++26)(C++26)(C++26)(C++26)

 bit width of unsigned char, unsigned short, unsigned int, unsigned long, and unsigned long long respectively
(macro constant) [edit]

UCHAR_MAXUSHRT_MAXUINT_MAXULONG_MAXULLONG_MAX

(C++11)

 maximum value of unsigned char, unsigned short, unsigned int,
unsigned long and unsigned long long respectively
(macro constant) [edit]

Defined in header <cwchar>

Defined in header <cstdint>

WCHAR_WIDTH

(C++26)

 bit width of wchar_t
(macro constant) [edit]

WCHAR_MIN

(C++11)

 minimum value of wchar_t
(macro constant) [edit]

WCHAR_MAX

(C++11)

 maximum value of wchar_t
(macro constant) [edit]
Characteristics of library type aliases

Defined in header <cstdint>

PTRDIFF_WIDTH

(C++26)

 bit width of std::ptrdiff_t
(macro constant) [edit]

PTRDIFF_MIN

(C++11)

 minimum value of std::ptrdiff_t
(macro constant) [edit]

PTRDIFF_MAX

(C++11)

 maximum value of std::ptrdiff_t
(macro constant) [edit]

SIZE_WIDTH

(C++26)

 bit width of std::size_t
(macro constant) [edit]

SIZE_MAX

(C++11)

 maximum value of std::size_t
(macro constant) [edit]

SIG_ATOMIC_WIDTH

(C++26)

 bit width of std::sig_atomic_t
(macro constant) [edit]

SIG_ATOMIC_MIN

(C++11)

 minimum value of std::sig_atomic_t
(macro constant) [edit]

SIG_ATOMIC_MAX

(C++11)

 maximum value of std::sig_atomic_t
(macro constant) [edit]

WINT_WIDTH

(C++26)

 bit width of std::wint_t
(macro constant) [edit]

WINT_MIN

(C++11)

 minimum value of std::wint_t
(macro constant) [edit]

WINT_MAX

(C++11)

 maximum value of std::wint_t
(macro constant) [edit]

Value requirements

BOOL_WIDTH always expands to 1.

(since C++26)

Each of the *_WIDTH macros (other than BOOL_WIDTH),(since C++26) CHAR_BIT and MB_LEN_MAX expands to an implementation-defined value. The allowed minimum values are listed below, where each group of macros separated by / always expand to the same value:

  • at least 1: MB_LEN_MAX
  • at least 8: CHAR_BIT / CHAR_WIDTH / SCHAR_WIDTH / UCHAR_WIDTH, WCHAR_WIDTH, SIG_ATOMIC_WIDTH
  • at least 16: SHRT_WIDTH / USHRT_WIDTH, INT_WIDTH / UINT_WIDTH, PTRDIFF_WIDTH, SIZE_WIDTH, WINT_WIDTH
  • at least 32: LONG_WIDTH / ULONG_WIDTH
  • at least 64: LLONG_WIDTH / ULLONG_WIDTH

Notes

The types of these constants, other than the *_WIDTH macros, (since C++26)CHAR_BIT and MB_LEN_MAX, are required to match the results of the integral promotions as applied to objects of the types they describe: CHAR_MAX may have type int or unsigned int, but never char. Similarly USHRT_MAX may not be of an unsigned type: its type may be int.

A freestanding implementation may lack std::sig_atomic_t and/or std::wint_t typedef names, in which case the SIG_ATOMIC_* and/or WINT_* macros are correspondingly absent.

Example

#include <climits>
#include <cstdint>
#include <iomanip>
#include <iostream>
#include <locale>

int main()
{
    constexpr int w = 14;
    (std::cout << std::left).imbue(std::locale("en_US.UTF-8"));
#   define COUT(x) std::cout << std::setw(w) << #x << " = " << x << '\n'
    
    COUT( BOOL_WIDTH     );
    COUT( CHAR_BIT       );
    COUT( CHAR_MAX       );
    COUT( CHAR_MIN       );
    COUT( CHAR_WIDTH     );
    COUT( INT_MAX        );
    COUT( INT_MIN        );
    COUT( INT_WIDTH      );
    COUT( LLONG_MAX      );
    COUT( LLONG_MIN      );
    COUT( LLONG_WIDTH    );
    COUT( LONG_MAX       );
    COUT( LONG_MIN       );
    COUT( LONG_WIDTH     );
    COUT( MB_LEN_MAX     );
    COUT( PTRDIFF_MAX    );
    COUT( PTRDIFF_MIN    );
    COUT( SCHAR_MAX      );
    COUT( SCHAR_MIN      );
    COUT( SCHAR_WIDTH    );
    COUT( SHRT_MAX       );
    COUT( SHRT_MIN       );
    COUT( SHRT_WIDTH     );
    COUT( SIG_ATOMIC_MAX );
    COUT( SIG_ATOMIC_MIN );
    COUT( SIZE_MAX       );
    COUT( UCHAR_MAX      );
    COUT( UCHAR_WIDTH    );
    COUT( UINT_MAX       );
    COUT( UINT_WIDTH     );
    COUT( ULLONG_MAX     );
    COUT( ULLONG_WIDTH   );
    COUT( ULONG_MAX      );
    COUT( ULONG_WIDTH    );
    COUT( USHRT_MAX      );
    COUT( USHRT_WIDTH    );
    COUT( WCHAR_MAX      );
    COUT( WCHAR_MIN      );
    COUT( WINT_MAX       );
    COUT( WINT_MIN       );
}

Possible output: 

BOOL_WIDTH     = 1
CHAR_BIT       = 8
CHAR_MAX       = 127
CHAR_MIN       = -128
CHAR_WIDTH     = 8
INT_MAX        = 2,147,483,647
INT_MIN        = -2,147,483,648
INT_WIDTH      = 32
LLONG_MAX      = 9,223,372,036,854,775,807
LLONG_MIN      = -9,223,372,036,854,775,808
LLONG_WIDTH    = 64
LONG_MAX       = 9,223,372,036,854,775,807
LONG_MIN       = -9,223,372,036,854,775,808
LONG_WIDTH     = 64
MB_LEN_MAX     = 16
PTRDIFF_MAX    = 9,223,372,036,854,775,807
PTRDIFF_MIN    = -9,223,372,036,854,775,808
SCHAR_MAX      = 127
SCHAR_MIN      = -128
SCHAR_WIDTH    = 8
SHRT_MAX       = 32,767
SHRT_MIN       = -32,768
SHRT_WIDTH     = 16
SIG_ATOMIC_MAX = 2,147,483,647
SIG_ATOMIC_MIN = -2,147,483,648
SIZE_MAX       = 18,446,744,073,709,551,615
UCHAR_MAX      = 255
UCHAR_WIDTH    = 8
UINT_MAX       = 4,294,967,295
UINT_WIDTH     = 32
ULLONG_MAX     = 18,446,744,073,709,551,615
ULLONG_WIDTH   = 64
ULONG_MAX      = 18,446,744,073,709,551,615
ULONG_WIDTH    = 64
USHRT_MAX      = 65,535
USHRT_WIDTH    = 16
WCHAR_MAX      = 2,147,483,647
WCHAR_MIN      = -2,147,483,648
WINT_MAX       = 4,294,967,295
WINT_MIN       = 0

Characteristics and special values of floating-point types

Characteristics of floating-point types
default rounding mode of floating-point arithmetic
(macro constant) [edit]
specifies in what precision all arithmetic operations are done
(macro constant) [edit]

FLT_HAS_SUBNORMDBL_HAS_SUBNORMLDBL_HAS_SUBNORM

(C++17)(deprecated in C++26)

 specifies whether the type supports subnormal (denormal) numbers:
-1 – indeterminable, 0 – absent, 1 – present
(macro constant) [edit]
the radix (integer base) used by the representation of all three floating-point types
(macro constant) [edit]

FLT_MANT_DIGDBL_MANT_DIGLDBL_MANT_DIG

 number of base FLT_RADIX digits that can be represented without losing precision for float, double and long double respectively
(macro constant) [edit]

FLT_DECIMAL_DIGDBL_DECIMAL_DIGLDBL_DECIMAL_DIG

(C++17)

 conversion from float/double/long double to decimal with at least FLT_DECIMAL_DIG/DBL_DECIMAL_DIG/LDBL_DECIMAL_DIG digits and back is the identity conversion: this is the decimal precision required to serialize/deserialize a floating-point value
(macro constant) [edit]

DECIMAL_DIG

(C++11)(deprecated in C++26)

 conversion from long double to decimal with at least DECIMAL_DIG digits and back to long double is the identity conversion: this is the decimal precision required to serialize/deserialize a long double
(macro constant) [edit]

FLT_DIGDBL_DIGLDBL_DIG

 number of decimal digits that are guaranteed to be preserved in text → float/double/long double → text roundtrip without change due to rounding or overflow
(macro constant) [edit]

FLT_MIN_EXPDBL_MIN_EXPLDBL_MIN_EXP

 minimum negative integer such that FLT_RADIX raised by power one less than that integer is a normalized float, double and long double respectively
(macro constant) [edit]

FLT_MIN_10_EXPDBL_MIN_10_EXPLDBL_MIN_10_EXP

 minimum negative integer such that 10 raised to that power is a normalized float, double and long double respectively
(macro constant) [edit]

FLT_MAX_EXPDBL_MAX_EXPLDBL_MAX_EXP

 maximum positive integer such that FLT_RADIX raised by power one less than that integer is a representable finite float, double and long double respectively
(macro constant) [edit]

FLT_MAX_10_EXPDBL_MAX_10_EXPLDBL_MAX_10_EXP

 maximum positive integer such that 10 raised to that power is a representable finite float, double and long double respectively
(macro constant) [edit]

FLT_MAXDBL_MAXLDBL_MAX

 maximum finite value of float, double and long double respectively
(macro constant) [edit]

FLT_EPSILONDBL_EPSILONLDBL_EPSILON

 difference between 1.0 and the next representable value for float, double and long double respectively
(macro constant) [edit]

FLT_MINDBL_MINLDBL_MIN

 minimum normalized positive value of float, double and long double respectively
(macro constant) [edit]

FLT_TRUE_MINDBL_TRUE_MINLDBL_TRUE_MIN

(C++17)

 minimum positive value of float, double and long double respectively
(macro constant) [edit]
Special values of floating-point types

Defined in header <cmath>    (deprecated in C++26)

Defined in header <cfloat>  (since C++26)

(C++11)

 evaluates to positive infinity (if exists)
(macro constant) [edit]

(C++11)

 evaluates to a quiet NaN of type float (if exists)
(macro constant) [edit]

Defined in header <cfloat>

evaluates to a signaling NaN of float, double and long double respectively (if exists)
(macro constant) [edit]

Example

#include <cfloat>
#include <iomanip>
#include <iostream>

int main()
{
    int w = 16;
    std::cout << std::left; // std::cout << std::setprecision(53);
#   define COUT(x) std::cout << std::setw(w) << #x << " = " << x << '\n'
    
    COUT( FLT_RADIX        );
    COUT( DECIMAL_DIG      );
    COUT( FLT_DECIMAL_DIG  );
    COUT( DBL_DECIMAL_DIG  );
    COUT( LDBL_DECIMAL_DIG );
    COUT( FLT_MIN          );
    COUT( DBL_MIN          );
    COUT( LDBL_MIN         );
    COUT( FLT_TRUE_MIN     );
    COUT( DBL_TRUE_MIN     );
    COUT( LDBL_TRUE_MIN    );
    COUT( FLT_MAX          );
    COUT( DBL_MAX          );
    COUT( LDBL_MAX         );
    COUT( FLT_EPSILON      );
    COUT( DBL_EPSILON      );
    COUT( LDBL_EPSILON     );
    COUT( FLT_DIG          );
    COUT( DBL_DIG          );
    COUT( LDBL_DIG         );
    COUT( FLT_MANT_DIG     );
    COUT( DBL_MANT_DIG     );
    COUT( LDBL_MANT_DIG    );
    COUT( FLT_MIN_EXP      );
    COUT( DBL_MIN_EXP      );
    COUT( LDBL_MIN_EXP     );
    COUT( FLT_MIN_10_EXP   );
    COUT( DBL_MIN_10_EXP   );
    COUT( LDBL_MIN_10_EXP  );
    COUT( FLT_MAX_EXP      );
    COUT( DBL_MAX_EXP      );
    COUT( LDBL_MAX_EXP     );
    COUT( FLT_MAX_10_EXP   );
    COUT( DBL_MAX_10_EXP   );
    COUT( LDBL_MAX_10_EXP  );
    COUT( FLT_ROUNDS       );
    COUT( FLT_EVAL_METHOD  );
    COUT( FLT_HAS_SUBNORM  );
    COUT( DBL_HAS_SUBNORM  );
    COUT( LDBL_HAS_SUBNORM );
}

Possible output: 

FLT_RADIX        = 2
DECIMAL_DIG      = 21
FLT_DECIMAL_DIG  = 9
DBL_DECIMAL_DIG  = 17
LDBL_DECIMAL_DIG = 21
FLT_MIN          = 1.17549e-38
DBL_MIN          = 2.22507e-308
LDBL_MIN         = 3.3621e-4932
FLT_TRUE_MIN     = 1.4013e-45
DBL_TRUE_MIN     = 4.94066e-324
LDBL_TRUE_MIN    = 3.6452e-4951
FLT_MAX          = 3.40282e+38
DBL_MAX          = 1.79769e+308
LDBL_MAX         = 1.18973e+4932
FLT_EPSILON      = 1.19209e-07
DBL_EPSILON      = 2.22045e-16
LDBL_EPSILON     = 1.0842e-19
FLT_DIG          = 6
DBL_DIG          = 15
LDBL_DIG         = 18
FLT_MANT_DIG     = 24
DBL_MANT_DIG     = 53
LDBL_MANT_DIG    = 64
FLT_MIN_EXP      = -125
DBL_MIN_EXP      = -1021
LDBL_MIN_EXP     = -16381
FLT_MIN_10_EXP   = -37
DBL_MIN_10_EXP   = -307
LDBL_MIN_10_EXP  = -4931
FLT_MAX_EXP      = 128
DBL_MAX_EXP      = 1024
LDBL_MAX_EXP     = 16384
FLT_MAX_10_EXP   = 38
DBL_MAX_10_EXP   = 308
LDBL_MAX_10_EXP  = 4932
FLT_ROUNDS       = 1
FLT_EVAL_METHOD  = 0
FLT_HAS_SUBNORM  = 1
DBL_HAS_SUBNORM  = 1
LDBL_HAS_SUBNORM = 1

Defect reports

The following behavior-changing defect reports were applied retroactively to previously published C++ standards.

DR Applied to Behavior as published Correct behavior
LWG 416 C++98 it was unclear whether the types of the macros in <climits> are guaranteed
to match the type to which they refer (C++ refers to C, and C says no) 		clarified as not
guaranteed

See also