Numeric limits

Characteristics of integer types

Defined in header `<limits.h>`
Characteristics of core language integer types
BOOL_WIDTH (C23)	bit width of bool (macro constant)
CHAR_BIT	bit width of byte (macro constant)
MB_LEN_MAX	maximum number of bytes in a multibyte character (macro constant)
CHAR_WIDTH (C23)	bit width of char (macro constant)
CHAR_MIN	minimum value of char (macro constant)
CHAR_MAX	maximum value of char (macro constant)
SCHAR_WIDTHSHRT_WIDTHINT_WIDTHLONG_WIDTHLLONG_WIDTH (C23)(C23)(C23)(C23)(C23)	bit width of signedchar, short, int, long, and longlong respectively (macro constant)
SCHAR_MINSHRT_MININT_MINLONG_MINLLONG_MIN (C99)	minimum value of signedchar, short, int, long and longlong respectively (macro constant)
SCHAR_MAXSHRT_MAXINT_MAXLONG_MAXLLONG_MAX (C99)	maximum value of signedchar, short, int, long and longlong respectively (macro constant)
UCHAR_WIDTHUSHRT_WIDTHUINT_WIDTHULONG_WIDTHULLONG_WIDTH (C23)(C23)(C23)(C23)(C23)	bit width of unsignedchar, unsignedshort, unsignedint, unsignedlong, and unsignedlonglong respectively (macro constant)
UCHAR_MAXUSHRT_MAXUINT_MAXULONG_MAXULLONG_MAX (C99)	maximum value of unsignedchar, unsignedshort, unsignedint, unsignedlong and unsignedlonglong respectively (macro constant)
BITINT_MAXWIDTH (C23)	maximum width N supported by the declaration of a bit-precise integer in the type specifier _BitInt(N) (macro constant)
Characteristics of library type aliases
Defined in header `<stdint.h>`
PTRDIFF_WIDTH (C23)	bit width of `ptrdiff_t` (macro constant)
PTRDIFF_MIN (C99)	minimum value of `ptrdiff_t` (macro constant)
PTRDIFF_MAX (C99)	maximum value of `ptrdiff_t` (macro constant)
SIZE_WIDTH (C23)	bit width of `size_t` (macro constant)
SIZE_MAX (C99)	maximum value of `size_t` (macro constant)
SIG_ATOMIC_WIDTH (C23)	bit width of `sig_atomic_t` (macro constant)
SIG_ATOMIC_MIN (C99)	minimum value of `sig_atomic_t` (macro constant)
SIG_ATOMIC_MAX (C99)	maximum value of `sig_atomic_t` (macro constant)
WINT_WIDTH (C23)	bit width of `wint_t` (macro constant)
WINT_MIN (C99)	minimum value of `wint_t` (macro constant)
WINT_MAX (C99)	maximum value of `wint_t` (macro constant)
Defined in header `<wchar.h>`
Defined in header `<stdint.h>`
WCHAR_WIDTH (C23)	bit width of wchar_t (macro constant)
WCHAR_MIN (C99)	minimum value of wchar_t (macro constant)
WCHAR_MAX (C99)	maximum value of wchar_t (macro constant)

Value requirements

BOOL_WIDTH always expands to 1.

(since C23)

Each of the *_WIDTH macros (other than BOOL_WIDTH), BITINT_MAXWIDTH,(since C23) 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
at least ULLONG_WIDTH: BITINT_MAXWIDTH

Notes

The types of these constants, other than the *_WIDTH macros, (since C23)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 unsignedint, but never char. Similarly USHRT_MAX may not be of an unsigned type: its type may be int.

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

Example

#include <limits.h>
#include <stdint.h>
#include <stdio.h>

int main(void)
{
    printf("CHAR_BIT       = %d\n", CHAR_BIT);
    printf("MB_LEN_MAX     = %d\n\n", MB_LEN_MAX);
    
    printf("CHAR_MIN       = %+d\n", CHAR_MIN);
    printf("CHAR_MAX       = %+d\n", CHAR_MAX);
    printf("SCHAR_MIN      = %+d\n", SCHAR_MIN);
    printf("SCHAR_MAX      = %+d\n", SCHAR_MAX);
    printf("UCHAR_MAX      = %u\n\n", UCHAR_MAX);
    
    printf("SHRT_MIN       = %+d\n", SHRT_MIN);
    printf("SHRT_MAX       = %+d\n", SHRT_MAX);
    printf("USHRT_MAX      = %u\n\n", USHRT_MAX);
    
    printf("INT_MIN        = %+d\n", INT_MIN);
    printf("INT_MAX        = %+d\n", INT_MAX);
    printf("UINT_MAX       = %u\n\n", UINT_MAX);
    
    printf("LONG_MIN       = %+ld\n", LONG_MIN);
    printf("LONG_MAX       = %+ld\n", LONG_MAX);
    printf("ULONG_MAX      = %lu\n\n", ULONG_MAX);
    
    printf("LLONG_MIN      = %+lld\n", LLONG_MIN);
    printf("LLONG_MAX      = %+lld\n", LLONG_MAX);
    printf("ULLONG_MAX     = %llu\n\n", ULLONG_MAX);
    
    printf("PTRDIFF_MIN    = %td\n", PTRDIFF_MIN);
    printf("PTRDIFF_MAX    = %+td\n", PTRDIFF_MAX);
    printf("SIZE_MAX       = %zu\n", SIZE_MAX);
    printf("SIG_ATOMIC_MIN = %+jd\n",(intmax_t)SIG_ATOMIC_MIN);
    printf("SIG_ATOMIC_MAX = %+jd\n",(intmax_t)SIG_ATOMIC_MAX);
    printf("WCHAR_MIN      = %+jd\n",(intmax_t)WCHAR_MIN);
    printf("WCHAR_MAX      = %+jd\n",(intmax_t)WCHAR_MAX);
    printf("WINT_MIN       = %jd\n", (intmax_t)WINT_MIN);
    printf("WINT_MAX       = %jd\n", (intmax_t)WINT_MAX);
}

Possible output:

CHAR_BIT       = 8
MB_LEN_MAX     = 16

CHAR_MIN       = -128
CHAR_MAX       = +127
SCHAR_MIN      = -128
SCHAR_MAX      = +127
UCHAR_MAX      = 255

SHRT_MIN       = -32768
SHRT_MAX       = +32767
USHRT_MAX      = 65535

INT_MIN        = -2147483648
INT_MAX        = +2147483647
UINT_MAX       = 4294967295

LONG_MIN       = -9223372036854775808
LONG_MAX       = +9223372036854775807
ULONG_MAX      = 18446744073709551615

LLONG_MIN      = -9223372036854775808
LLONG_MAX      = +9223372036854775807
ULLONG_MAX     = 18446744073709551615

PTRDIFF_MIN    = -9223372036854775808
PTRDIFF_MAX    = +9223372036854775807
SIZE_MAX       = 18446744073709551615
SIG_ATOMIC_MIN = -2147483648
SIG_ATOMIC_MAX = +2147483647
WCHAR_MIN      = -2147483648
WCHAR_MAX      = +2147483647
WINT_MIN       = 0
WINT_MAX       = 4294967295

Characteristics and special values of floating-point types

Defined in header `<float.h>`
Characteristics of floating-point types
FLT_ROUNDS	default rounding mode of floating-point arithmetic (macro constant)
FLT_EVAL_METHOD (C99)	specifies in what precision all arithmetic operations are done (macro constant)

FLT_HAS_SUBNORMDBL_HAS_SUBNORMLDBL_HAS_SUBNORM

(C11)(deprecated in C23)

specifies whether the type supports subnormal (denormal) numbers:
-1 – indeterminable, 0 – absent, 1 – present
(macro constant)

FLT_RADIX	the radix (integer base) used by the representation of all three floating-point types (macro constant)
FLT_MANT_DIGDBL_MANT_DIGLDBL_MANT_DIG	number of base `FLT_RADIX` digits that can be represented without losing precision for float, double and longdouble respectively (macro constant)
FLT_DECIMAL_DIGDBL_DECIMAL_DIGLDBL_DECIMAL_DIG (C11)	conversion from float/double/longdouble 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)

DECIMAL_DIG

(C99)(deprecated in C23)

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

Defined in header `<math.h>` (deprecated in C23)
FLT_DIGDBL_DIGLDBL_DIG	number of decimal digits that are guaranteed to be preserved in text → float/double/longdouble → text roundtrip without change due to rounding or overflow (macro constant)
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)
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)
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)
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)
FLT_MAXDBL_MAXLDBL_MAX	maximum finite value of float, double and long double respectively (macro constant)
FLT_EPSILONDBL_EPSILONLDBL_EPSILON	difference between `1.0` and the next representable value for float, double and long double respectively (macro constant)
FLT_MINDBL_MINLDBL_MIN	minimum normalized positive value of float, double and long double respectively (macro constant)
FLT_TRUE_MINDBL_TRUE_MINLDBL_TRUE_MIN (C11)	minimum positive value of float, double and long double respectively (macro constant)
Special values of floating-point types
Defined in header `<float.h>` (since C23)
INFINITY (C99)	evaluates to positive infinity (if exists) (macro constant)
NAN (C99)	evaluates to a quiet NaN of type float (if exists) (macro constant)
Defined in header `<float.h>`
FLT_SNANDBL_SNANLDBL_SNAN (C23)	evaluates to a signaling NaN of float, double and long double respectively (if exists) (macro constant)

Example

#include <float.h>
#include <math.h>
#include <stdio.h>

int main(void)
{
    printf("DECIMAL_DIG     = %d\n", DECIMAL_DIG);
    printf("FLT_DECIMAL_DIG = %d\n", FLT_DECIMAL_DIG);
    printf("FLT_RADIX       = %d\n", FLT_RADIX);
    printf("FLT_MIN         = %e\n", FLT_MIN);
    printf("FLT_MAX         = %e\n", FLT_MAX);
    printf("FLT_EPSILON     = %e\n", FLT_EPSILON);
    printf("FLT_DIG         = %d\n", FLT_DIG);
    printf("FLT_MANT_DIG    = %d\n", FLT_MANT_DIG);
    printf("FLT_MIN_EXP     = %d\n", FLT_MIN_EXP);
    printf("FLT_MIN_10_EXP  = %d\n", FLT_MIN_10_EXP);
    printf("FLT_MAX_EXP     = %d\n", FLT_MAX_EXP);
    printf("FLT_MAX_10_EXP  = %d\n", FLT_MAX_10_EXP);
    printf("FLT_ROUNDS      = %d\n", FLT_ROUNDS);
    printf("FLT_EVAL_METHOD = %d\n", FLT_EVAL_METHOD);
    printf("FLT_HAS_SUBNORM = %d\n", FLT_HAS_SUBNORM);
}

Possible output:

DECIMAL_DIG     = 37
FLT_DECIMAL_DIG = 9
FLT_RADIX       = 2
FLT_MIN         = 1.175494e-38
FLT_MAX         = 3.402823e+38
FLT_EPSILON     = 1.192093e-07
FLT_DIG         = 6
FLT_MANT_DIG    = 24
FLT_MIN_EXP     = -125
FLT_MIN_10_EXP  = -37
FLT_MAX_EXP     = 128
FLT_MAX_10_EXP  = 38
FLT_ROUNDS      = 1
FLT_EVAL_METHOD = 1
FLT_HAS_SUBNORM = 1

References

C23 standard (ISO/IEC 9899:2024):

5.2.4.2 Numerical limits (p: TBD)
7.22.3 Limits of other integer types (p: TBD)

C17 standard (ISO/IEC 9899:2018):

5.2.4.2 Numerical limits (p: 20-27)
7.20.3 Limits of other integer types (p: 215-216)

C11 standard (ISO/IEC 9899:2011):

5.2.4.2 Numerical limits (p: 26-34)
7.20.3 Limits of other integer types (p: 293-294)

C99 standard (ISO/IEC 9899:1999):

5.2.4.2 Numerical limits (p: 21-28)
7.18.3 Limits of other integer types (p: 259-260)

C89/C90 standard (ISO/IEC 9899:1990):

2.2.4.2 Numerical limits

Numeric limits

Characteristics of integer types

Characteristics of core language integer types

Characteristics of library type aliases

Value requirements

Notes

Example

Characteristics and special values of floating-point types

Characteristics of floating-point types

Special values of floating-point types

Example

References

See also