Values of the complementary error function $\operatorname{erfc}(x)$
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Numbers
$x$ 
$\operatorname{erfc}(x)$
0:
1
$1/\sqrt{2}$:
0.3173105078629141028295349087359241550441740665467912180252110995140171160255903409982301631887213449
comment: The argument is specified by (8).
$2/\sqrt{2}$:
0.04550026389635841440056527433306687494355244740335686796733200026095258070555149669653830415157922985
comment: The argument is specified by (8).
$3/\sqrt{2}$:
0.002699796063260189053303629535189954755658736316761298728443970711611441529144200536077162572008434106
comment: The argument is specified by (8).
$4/\sqrt{2}$:
0.00006334248366623984250754151344430259688766675096055301709866344415717033825179660477182793534281581621
comment: The argument is specified by (8).
$5/\sqrt{2}$:
5.733031437583878233475046657492907077088460272237791461709855978695175398441279867277061766331145483e-7
comment: The argument is specified by (8).
$6/\sqrt{2}$:
1.973175290075396281401728264796084037339582499958057444954030432350931348485828336802407053630110350e-9
comment: The argument is specified by (8).
-1:
1.842700792949714869341220635082609259296066997966302908459937897834717254096010841261983325348144888
comment: A bounded Gaussian-integral reference; see (9).
-1/2:
1.520499877813046537682746653891964528736451575757963700058805725647193521716853570914788218734787757
comment: A bounded Gaussian-integral reference; see (9).
1/2:
0.4795001221869534623172533461080354712635484242420362999411942743528064782831464290852117812652122430
comment: A bounded Gaussian-integral reference; see (9).
1:
0.1572992070502851306587793649173907407039330020336970915400621021652827459039891587380166746518551115
comment: A bounded Gaussian-integral reference; see (9).
3/2:
0.03389485352468927293302373835405214131858952074236321955003215355786714557624927375513345071972281159
comment: A bounded Gaussian-integral reference; see (9).
2:
0.004677734981047265837930743632747071389108202959939923261647673799562719280004822632370991980319319512
comment: A bounded Gaussian-integral reference; see (9).
3:
0.00002209049699858544137277612958232037984770708739924965723895484294245668362013226781625465081531628714
comment: A bounded Gaussian-integral reference; see (9).
4:
1.541725790028001885215967348688404857214525358919116834290499421304102681125407276501345618058178859e-8
comment: A bounded Gaussian-integral reference; see (9).
$\sqrt{3}$:
0.01430587843542963952584780642225069357366252284955995429948134050553501431370759423343965102705568961
comment: An integer-coefficient Gaussian-integral reference; see (10).
$\sqrt{5}$:
0.001565402258002549677499803978385902310434574685982805342599726418084334477889667407474568646530340887
comment: An integer-coefficient Gaussian-integral reference; see (10).
$\sqrt{6}$:
0.0005320055051392496992898821332382937855793729475574940474614621251273456301614397843281499964174928270
comment: An integer-coefficient Gaussian-integral reference; see (10).
Definition
The complementary error function is $\operatorname{erfc}(x)=1-\operatorname{erf}(x)$ [4], the tail of the Gaussian. This table gives its values at intrinsic and bounded reference arguments.
Parameters
$x$
—   argument ($x\in\mathbb{R}$)
Formulas
(1)
For real $x$, $\operatorname{erf}(x)=\frac{2}{\sqrt{\pi}}\int_0^x e^{-t^2}\,\mathrm{d}t$, $\operatorname{erfc}(x)=1-\operatorname{erf}(x)$, and $\operatorname{erfi}(x)=-i\operatorname{erf}(ix)$ [4].
(2)
The functions $\operatorname{erf}$, $\operatorname{erfi}$, $F$, $S$ and $C$ are odd, and $\operatorname{erfc}(-x)=2-\operatorname{erfc}(x)$.
(3)
$\int_0^1e^{-nt^2}\,dt=\frac{\sqrt\pi}{2\sqrt n}[1-\operatorname{erfc}(\sqrt n)]$, $n>0$.
Comments
(4)
For large positive $x$, $\operatorname{erfc}(x)$ is the small tail $1-\operatorname{erf}(x)$.
(5)
The probability integral $\alpha(x)$ is $\operatorname{erf}(x/\sqrt{2})$ [5]. The standard-normal tail $Q(x)$ is $\tfrac12\operatorname{erfc}(x/\sqrt2)$ [1]. The curve $t\mapsto(C(t),S(t))$ is Cornu's spiral, also called the Euler spiral or clothoid, for this Fresnel normalisation [6] [3].
(6)
Negative arguments are not listed separately. Values at negative arguments follow from (2).
(7)
At $x=0$ the value is exact, $\operatorname{erfc}(0)=1$, and is stored as the integer rather than as a hundred places of one.
(8)
For a standard normal random variable $Z$, $\Pr(|Z|\leq n)=\operatorname{erf}(n/\sqrt2)$ and $\Pr(|Z|>n)=\operatorname{erfc}(n/\sqrt2)$ [7]. Integer standard-deviation thresholds select these arguments. They are conventional probability references, not arbitrary probability quantiles or mathematically unique cutoffs.
(9)
The simple inputs $x=-1,-1/2,1/2,1,3/2,2,3,4$ supplement the conventional standard-deviation references. They are a bounded exploratory Gaussian-integral reference, including negative-side reflection examples and moderate positive tails, not quantile cutoffs [8].
(10)
Integer quadratic coefficients in the truncated Gaussian integral $\int_0^1e^{-nt^2}\,dt$ select $x=\sqrt n$. The exploratory range $1\leq n\leq6$ is finite and noncanonical; coincident arguments such as $\sqrt2=2/\sqrt2$ are represented only once [8].
(11)
The current generate.py reproduces the complete attached selection, including the retained entries. Their original written values and entry comments are preserved rather than reassigned to a new source. The selection manifest records the predecessor revision and source hashes; earlier generators and checks remain historical provenance, not the enumeration of this extension.
Programs
(P1)
Python
from generate import generator
from numberdb._write import to_text

for params, result in generator.all_entries():
    print(params["x"], to_text(result["number"], generator.digits_for(params)))
Links
Similar tables
Values of the error function $\operatorname{erf}(x)$ —   $\operatorname{erfc}=1-\operatorname{erf}$
Values of the imaginary error function $\operatorname{erfi}(x)$ —   another member of the error-function family
Values of Dawson's integral $F(x)$ —   another member of the error-function family
Values of the Fresnel sine integral $S(x)$ —   another member of the error-function family
Values of the Fresnel cosine integral $C(x)$ —   another member of the error-function family
Values of the exponential integral —   stores $\operatorname{Ei}(x)$ and $E_1(x)$, with exponential kernels $e^t/t$ and $e^{-t}/t$ rather than the Gaussian kernel $e^{-t^2}$
Values of the sine integral $\operatorname{Si}(x)$ —   stores $\operatorname{Si}(x)=\int_0^x\sin(t)/t\,\mathrm{d}t$, with linear phase in place of the Fresnel quadratic phase
Values of the cosine integral $\operatorname{Ci}(x)$ —   stores $\operatorname{Ci}(x)=\gamma+\log x+\int_0^x(\cos(t)-1)/t\,\mathrm{d}t$, with linear phase in place of the Fresnel quadratic phase
Values of the hyperbolic sine integral $\operatorname{Shi}(x)$ —   stores $\operatorname{Shi}(x)=\int_0^x\sinh(t)/t\,\mathrm{d}t$ at rational arguments
Values of the hyperbolic cosine integral $\operatorname{Chi}(x)$ —   stores $\operatorname{Chi}(x)=\gamma+\log x+\int_0^x(\cosh(t)-1)/t\,\mathrm{d}t$ at rational arguments
Values of the Gamma function at rational numbers —   contains $\Gamma(1/2)=\sqrt{\pi}$, the normalising constant in $\operatorname{erf}$ and $\operatorname{erfc}$
Data properties
Entries are of type: real number
Table is complete: no (it holds the origin and the one- through six-standard-deviation references $x=n/\sqrt2$, $1\leq n\leq6$, under (8); the selection is not exhaustive over the real domain. In addition, it includes the simple inputs $-1,-1/2,1/2,1,3/2,2,3,4$ and $\sqrt n$ for $1\leq n\leq6$, counting equivalent arguments only once. The exploratory families are identification references with practical finite bounds, not claims of documented applications for every input. All prior entries are retained.)
How they were obtained:

All retained values and metadata are preserved, including their precision. New nonexact values have 100 significant digits. balanced_values.py reproduces the complete selection in balanced-selection.json with Arb balls, including uncertainty in exact irrational arguments and certified roots. A 640-bit guard is supplemented by measured accuracy checks and precision escalation.

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Every written interval contains a freshly recomputed certified enclosure; every value is also checked with independent mpmath computations at 50 and 100 decimal guard digits. Exact origin anchors stay exact. Structural identities, root endpoint signs where applicable, and selected transformed definite integrals supplement these checks. See balanced-checks-evidence.json. Earlier checks-evidence.json and source attachments describe earlier selections and remain for provenance.