diff --git a/calc.go b/calc.go
index 59d97e04..fa6ec0a8 100644
--- a/calc.go
+++ b/calc.go
@@ -506,6 +506,8 @@ type formulaFuncs struct {
 //    VLOOKUP
 //    XOR
 //    YEAR
+//    Z.TEST
+//    ZTEST
 //
 func (f *File) CalcCellValue(sheet, cell string) (result string, err error) {
 	var (
@@ -5612,6 +5614,61 @@ func (fn *formulaFuncs) VARdotP(argsList *list.List) formulaArg {
 	return fn.VARP(argsList)
 }
 
+// ZdotTEST function calculates the one-tailed probability value of the
+// Z-Test. The syntax of the function is:
+//
+//    Z.TEST(array,x,[sigma])
+//
+func (fn *formulaFuncs) ZdotTEST(argsList *list.List) formulaArg {
+	argsLen := argsList.Len()
+	if argsLen < 2 {
+		return newErrorFormulaArg(formulaErrorVALUE, "Z.TEST requires at least 2 arguments")
+	}
+	if argsLen > 3 {
+		return newErrorFormulaArg(formulaErrorVALUE, "Z.TEST accepts at most 3 arguments")
+	}
+	return fn.ZTEST(argsList)
+}
+
+// ZTEST function calculates the one-tailed probability value of the Z-Test.
+// The syntax of the function is:
+//
+//    ZTEST(array,x,[sigma])
+//
+func (fn *formulaFuncs) ZTEST(argsList *list.List) formulaArg {
+	argsLen := argsList.Len()
+	if argsLen < 2 {
+		return newErrorFormulaArg(formulaErrorVALUE, "ZTEST requires at least 2 arguments")
+	}
+	if argsLen > 3 {
+		return newErrorFormulaArg(formulaErrorVALUE, "ZTEST accepts at most 3 arguments")
+	}
+	arrArg, arrArgs := argsList.Front().Value.(formulaArg), list.New()
+	arrArgs.PushBack(arrArg)
+	arr := fn.AVERAGE(arrArgs)
+	if arr.Type == ArgError {
+		return newErrorFormulaArg(formulaErrorNA, formulaErrorNA)
+	}
+	x := argsList.Front().Next().Value.(formulaArg).ToNumber()
+	if x.Type == ArgError {
+		return x
+	}
+	sigma := argsList.Back().Value.(formulaArg).ToNumber()
+	if sigma.Type == ArgError {
+		return sigma
+	}
+	if argsLen != 3 {
+		sigma = fn.STDEV(arrArgs).ToNumber()
+	}
+	normsdistArg := list.New()
+	div := sigma.Number / math.Sqrt(float64(len(arrArg.ToList())))
+	if div == 0 {
+		return newErrorFormulaArg(formulaErrorDIV, formulaErrorDIV)
+	}
+	normsdistArg.PushBack(newNumberFormulaArg((arr.Number - x.Number) / div))
+	return newNumberFormulaArg(1 - fn.NORMSDIST(normsdistArg).Number)
+}
+
 // Information Functions
 
 // ISBLANK function tests if a specified cell is blank (empty) and if so,
diff --git a/calc_test.go b/calc_test.go
index cd09e972..7018ee92 100644
--- a/calc_test.go
+++ b/calc_test.go
@@ -1899,6 +1899,20 @@ func TestCalcCellValue(t *testing.T) {
 		// VAR.P
 		"=VAR.P()":     "VAR.P requires at least 1 argument",
 		"=VAR.P(\"\")": "#DIV/0!",
+		// Z.TEST
+		"Z.TEST(A1)":        "Z.TEST requires at least 2 arguments",
+		"Z.TEST(A1,0,0,0)":  "Z.TEST accepts at most 3 arguments",
+		"Z.TEST(H1,0)":      "#N/A",
+		"Z.TEST(A1,\"\")":   "strconv.ParseFloat: parsing \"\": invalid syntax",
+		"Z.TEST(A1,1)":      "#DIV/0!",
+		"Z.TEST(A1,1,\"\")": "strconv.ParseFloat: parsing \"\": invalid syntax",
+		// ZTEST
+		"ZTEST(A1)":        "ZTEST requires at least 2 arguments",
+		"ZTEST(A1,0,0,0)":  "ZTEST accepts at most 3 arguments",
+		"ZTEST(H1,0)":      "#N/A",
+		"ZTEST(A1,\"\")":   "strconv.ParseFloat: parsing \"\": invalid syntax",
+		"ZTEST(A1,1)":      "#DIV/0!",
+		"ZTEST(A1,1,\"\")": "strconv.ParseFloat: parsing \"\": invalid syntax",
 		// Information Functions
 		// ISBLANK
 		"=ISBLANK(A1,A2)": "ISBLANK requires 1 argument",
@@ -2759,6 +2773,25 @@ func TestCalcMATCH(t *testing.T) {
 	assert.Equal(t, newErrorFormulaArg(formulaErrorNA, formulaErrorNA), calcMatch(2, nil, []formulaArg{}))
 }
 
+func TestCalcZTEST(t *testing.T) {
+	f := NewFile()
+	assert.NoError(t, f.SetSheetRow("Sheet1", "A1", &[]int{4, 5, 2, 5, 8, 9, 3, 2, 3, 8, 9, 5}))
+	formulaList := map[string]string{
+		"=Z.TEST(A1:L1,5)":   "0.371103278558538",
+		"=Z.TEST(A1:L1,6)":   "0.838129187019751",
+		"=Z.TEST(A1:L1,5,1)": "0.193238115385616",
+		"=ZTEST(A1:L1,5)":    "0.371103278558538",
+		"=ZTEST(A1:L1,6)":    "0.838129187019751",
+		"=ZTEST(A1:L1,5,1)":  "0.193238115385616",
+	}
+	for formula, expected := range formulaList {
+		assert.NoError(t, f.SetCellFormula("Sheet1", "M1", formula))
+		result, err := f.CalcCellValue("Sheet1", "M1")
+		assert.NoError(t, err, formula)
+		assert.Equal(t, expected, result, formula)
+	}
+}
+
 func TestStrToDate(t *testing.T) {
 	_, _, _, _, err := strToDate("")
 	assert.Equal(t, formulaErrorVALUE, err.Error)