# ceil, ceilf, ceill

< c‎ | numeric‎ | math

Common mathematical functions
Types
 div_tldiv_tlldiv_timaxdiv_t(C99)(C99)
 float_tdouble_t(C99)(C99) _Decimal32_t_Decimal64_t(C23)(C23)
Functions
Basic operations
 abslabsllabsimaxabs(C99)(C99) fabs divldivlldivimaxdiv(C99)(C99)
 fmod remainder(C99) remquo(C99) fma(C99) fdim(C99) nannanfnanlnandN(C99)(C99)(C99)(C23)
Maximum/minimum operations
 fmax(C99) fmaximum(C23) fmaximum_mag(C23) fmaximum_num(C23) fmaximum_mag_num(C23)
 fmin(C99) fminimum(C23) fminimum_mag(C23) fminimum_num(C23) fminimum_mag_num(C23)
Exponential functions
 exp exp10(C23) exp2(C99) expm1(C99) exp10m1(C23) exp2m1(C23)
 log log10 log2(C99) log1plogp1(C99)(C23) log10p1(C23) log2p1(C23)
Power functions
 sqrt cbrt(C99) rootn(C23) rsqrt(C23)
 hypot(C99) compound(C23) pow pown(C23) powr(C23)
Trigonometric and hyperbolic functions
 sin cos tan asin acos atan atan2 sinpi(C23) cospi(C23) tanpi(C23)
 asinpi(C23) acospi(C23) atanpi(C23) atan2pi(C23) sinh cosh tanh asinh(C99) acosh(C99) atanh(C99)
Error and gamma functions
 erf(C99) erfc(C99)
 lgamma(C99) tgamma(C99)
Nearest integer floating-point operations
 ceil floor roundlroundllround(C99)(C99)(C99) roundeven(C23) trunc(C99)
 nearbyint(C99) rintlrintllrint(C99)(C99)(C99) fromfpfromfpxufromfpufromfpx(C23)(C23)(C23)(C23)
Floating-point manipulation functions
 ldexp frexp scalbnscalbln(C99)(C99) ilogbllogb(C99)(C23) logb(C99)
 modf nextafternexttoward(C99)(C99) nextupnextdown(C23)(C23) copysign(C99) canonicalize(C23)
Narrowing operations
 fdiv(C23) ffma(C23) fsqrt(C23)
Quantum and quantum exponent functions
 quantizedN(C23) samequantumdN(C23)
 quantumdN(C23) llquantexpdN(C23)
Decimal re-encoding functions
 encodedecdN(C23) decodedecdN(C23)
 encodebindN(C23) decodebindN(C23)
Total order and payload functions
Classification
 fpclassify(C99) iscanonical(C23) isfinite(C99) isinf(C99) isnan(C99) isnormal(C99) signbit(C99) issubnormal(C23) iszero(C23)
 isgreater(C99) isgreaterequal(C99) isless(C99) islessequal(C99) islessgreater(C99) isunordered(C99) issignaling(C23) iseqsig(C23)
Macro constants
Special floating-point values
 HUGE_VALFHUGE_VALHUGE_VALLHUGE_VALDN(C99)(C99)(C23)
 INFINITYDEC_INFINITY(C99)(C23) NANDEC_NAN(C99)(C23)
Arguments and return values
 FP_ILOGB0FP_ILOGBNAN(C99)(C99) FP_INT_UPWARDFP_INT_DOWNWARDFP_INT_TOWARDZEROFP_INT_TONEARESTFROMZEROFP_INT_TONEAREST(C23)(C23)(C23)(C23)(C23)
 FP_LLOGB0FP_LLOGBNAN(C23)(C23) FP_NORMALFP_SUBNORMALFP_ZEROFP_INFINITEFP_NAN(C99)(C99)(C99)(C99)(C99)
Error handling
 MATH_ERRNOMATH_ERRNOEXCEPT(C99)(C99)
 math_errhandling(C99)
Fast operation indicators
 FP_FAST_FMALFP_FAST_FMADN(C99)(C23) FP_FAST_FSUBFP_FAST_FSUBLFP_FAST_DSUBLFP_FAST_DMSUBDN(C23)(C23)(C23)(C23) FP_FAST_FDIVFP_FAST_FDIVLFP_FAST_DDIVLFP_FAST_DMDIVDN(C23)(C23)(C23)(C23) FP_FAST_FSQRTFP_FAST_FSQRTLFP_FAST_DSQRTLFP_FAST_DMSQRTDN(C23)(C23)(C23)(C23)

 Defined in header  float       ceilf( float arg ); (1) (since C99) double      ceil( double arg ); (2) long double ceill( long double arg ); (3) (since C99) Defined in header  #define ceil( arg ) (4) (since C99)
1-3) Computes the smallest integer value not less than arg.
4) Type-generic macro: If arg has type long double, ceill is called. Otherwise, if arg has integer type or the type double, ceil is called. Otherwise, ceilf is called.

## Contents

### Parameters

 arg - floating-point value

### Return value

If no errors occur, the smallest integer value not less than arg, that is ⌈arg⌉, is returned.

Return value
Argument

### Error handling

Errors are reported as specified in math_errhandling.

If the implementation supports IEEE floating-point arithmetic (IEC 60559):

• The current rounding mode has no effect.
• If arg is ±∞, it is returned, unmodified.
• If arg is ±0, it is returned, unmodified.
• If arg is NaN, NaN is returned.

### Notes

FE_INEXACT may be (but isn't required to be) raised when rounding a non-integer finite value.

The largest representable floating-point values are exact integers in all standard floating-point formats, so this function never overflows on its own; however the result may overflow any integer type (including intmax_t), when stored in an integer variable.

This function (for double argument) behaves as if (except for the freedom to not raise FE_INEXACT) implemented by

#include <fenv.h>
#include <math.h>
#pragma STDC FENV_ACCESS ON

double ceil(double x)
{
double result;
int save_round = fegetround();
fesetround(FE_UPWARD);
result = rint(x); // or nearbyint
fesetround(save_round);
return result;
}

### Example

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

int main(void)
{
printf("ceil(+2.4) = %+.1f\n", ceil(2.4));
printf("ceil(-2.4) = %+.1f\n", ceil(-2.4));
printf("ceil(-0.0) = %+.1f\n", ceil(-0.0));
printf("ceil(-Inf) = %+f\n",   ceil(-INFINITY));
}

Possible output:

ceil(+2.4) = +3.0
ceil(-2.4) = -2.0
ceil(-0.0) = -0.0
ceil(-Inf) = -inf

### References

• C23 standard (ISO/IEC 9899:2024):
• 7.12.9.1 The ceil functions (p: TBD)
• 7.25 Type-generic math <tgmath.h> (p: TBD)
• F.10.6.1 The ceil functions (p: TBD)
• C17 standard (ISO/IEC 9899:2018):
• 7.12.9.1 The ceil functions (p: TBD)
• 7.25 Type-generic math <tgmath.h> (p: TBD)
• F.10.6.1 The ceil functions (p: TBD)
• C11 standard (ISO/IEC 9899:2011):
• 7.12.9.1 The ceil functions (p: 251)
• 7.25 Type-generic math <tgmath.h> (p: 373-375)
• F.10.6.1 The ceil functions (p: 526)
• C99 standard (ISO/IEC 9899:1999):
• 7.12.9.1 The ceil functions (p: 231-232)
• 7.22 Type-generic math <tgmath.h> (p: 335-337)
• F.9.6.1 The ceil functions (p: 462-463)
• C89/C90 standard (ISO/IEC 9899:1990):
• 4.5.6.1 The ceil function