diff --git a/calc.go b/calc.go
index 385503f..51a830e 100644
--- a/calc.go
+++ b/calc.go
@@ -554,6 +554,8 @@ type formulaFuncs struct {
 //    XOR
 //    YEAR
 //    YEARFRAC
+//    YIELDDISC
+//    YIELDMAT
 //    Z.TEST
 //    ZTEST
 //
@@ -9705,3 +9707,114 @@ func (fn *formulaFuncs) SYD(argsList *list.List) formulaArg {
 	}
 	return newNumberFormulaArg(((cost.Number - salvage.Number) * (life.Number - per.Number + 1) * 2) / (life.Number * (life.Number + 1)))
 }
+
+// YIELDDISC function calculates the annual yield of a discounted security.
+// The syntax of the function is:
+//
+//    YIELDDISC(settlement,maturity,pr,redemption,[basis])
+//
+func (fn *formulaFuncs) YIELDDISC(argsList *list.List) formulaArg {
+	if argsList.Len() != 4 && argsList.Len() != 5 {
+		return newErrorFormulaArg(formulaErrorVALUE, "YIELDDISC requires 4 or 5 arguments")
+	}
+	args := list.New().Init()
+	args.PushBack(argsList.Front().Value.(formulaArg))
+	settlement := fn.DATEVALUE(args)
+	if settlement.Type != ArgNumber {
+		return newErrorFormulaArg(formulaErrorVALUE, formulaErrorVALUE)
+	}
+	args.Init()
+	args.PushBack(argsList.Front().Next().Value.(formulaArg))
+	maturity := fn.DATEVALUE(args)
+	if maturity.Type != ArgNumber {
+		return newErrorFormulaArg(formulaErrorVALUE, formulaErrorVALUE)
+	}
+	pr := argsList.Front().Next().Next().Value.(formulaArg).ToNumber()
+	if pr.Type != ArgNumber {
+		return newErrorFormulaArg(formulaErrorVALUE, formulaErrorVALUE)
+	}
+	if pr.Number <= 0 {
+		return newErrorFormulaArg(formulaErrorNUM, "YIELDDISC requires pr > 0")
+	}
+	redemption := argsList.Front().Next().Next().Next().Value.(formulaArg).ToNumber()
+	if redemption.Type != ArgNumber {
+		return newErrorFormulaArg(formulaErrorVALUE, formulaErrorVALUE)
+	}
+	if redemption.Number <= 0 {
+		return newErrorFormulaArg(formulaErrorNUM, "YIELDDISC requires redemption > 0")
+	}
+	basis := newNumberFormulaArg(0)
+	if argsList.Len() == 5 {
+		if basis = argsList.Back().Value.(formulaArg).ToNumber(); basis.Type != ArgNumber {
+			return newErrorFormulaArg(formulaErrorNUM, formulaErrorNUM)
+		}
+	}
+	frac := yearFrac(settlement.Number, maturity.Number, int(basis.Number))
+	if frac.Type != ArgNumber {
+		return frac
+	}
+	return newNumberFormulaArg((redemption.Number/pr.Number - 1) / frac.Number)
+}
+
+// YIELDMAT function calculates the annual yield of a security that pays
+// interest at maturity. The syntax of the function is:
+//
+//    YIELDMAT(settlement,maturity,issue,rate,pr,[basis])
+//
+func (fn *formulaFuncs) YIELDMAT(argsList *list.List) formulaArg {
+	if argsList.Len() != 5 && argsList.Len() != 6 {
+		return newErrorFormulaArg(formulaErrorVALUE, "YIELDMAT requires 5 or 6 arguments")
+	}
+	args := list.New().Init()
+	args.PushBack(argsList.Front().Value.(formulaArg))
+	settlement := fn.DATEVALUE(args)
+	if settlement.Type != ArgNumber {
+		return newErrorFormulaArg(formulaErrorVALUE, formulaErrorVALUE)
+	}
+	args.Init()
+	args.PushBack(argsList.Front().Next().Value.(formulaArg))
+	maturity := fn.DATEVALUE(args)
+	if maturity.Type != ArgNumber {
+		return newErrorFormulaArg(formulaErrorVALUE, formulaErrorVALUE)
+	}
+	args.Init()
+	args.PushBack(argsList.Front().Next().Next().Value.(formulaArg))
+	issue := fn.DATEVALUE(args)
+	if issue.Type != ArgNumber {
+		return newErrorFormulaArg(formulaErrorVALUE, formulaErrorVALUE)
+	}
+	if issue.Number >= settlement.Number {
+		return newErrorFormulaArg(formulaErrorNUM, "YIELDMAT requires settlement > issue")
+	}
+	rate := argsList.Front().Next().Next().Next().Value.(formulaArg).ToNumber()
+	if rate.Type != ArgNumber {
+		return rate
+	}
+	if rate.Number < 0 {
+		return newErrorFormulaArg(formulaErrorNUM, "YIELDMAT requires rate >= 0")
+	}
+	pr := argsList.Front().Next().Next().Next().Next().Value.(formulaArg).ToNumber()
+	if pr.Type != ArgNumber {
+		return pr
+	}
+	if pr.Number <= 0 {
+		return newErrorFormulaArg(formulaErrorNUM, "YIELDMAT requires pr > 0")
+	}
+	basis := newNumberFormulaArg(0)
+	if argsList.Len() == 6 {
+		if basis = argsList.Back().Value.(formulaArg).ToNumber(); basis.Type != ArgNumber {
+			return newErrorFormulaArg(formulaErrorNUM, formulaErrorNUM)
+		}
+	}
+	dim := yearFrac(issue.Number, maturity.Number, int(basis.Number))
+	if dim.Type != ArgNumber {
+		return dim
+	}
+	dis := yearFrac(issue.Number, settlement.Number, int(basis.Number))
+	dsm := yearFrac(settlement.Number, maturity.Number, int(basis.Number))
+	result := 1 + dim.Number*rate.Number
+	result /= pr.Number/100 + dis.Number*rate.Number
+	result--
+	result /= dsm.Number
+	return newNumberFormulaArg(result)
+}
diff --git a/calc_test.go b/calc_test.go
index 2412615..1df622e 100644
--- a/calc_test.go
+++ b/calc_test.go
@@ -1354,6 +1354,12 @@ func TestCalcCellValue(t *testing.T) {
 		// SYD
 		"=SYD(10000,1000,5,1)": "3000",
 		"=SYD(10000,1000,5,2)": "2400",
+		// YIELDDISC
+		"=YIELDDISC(\"01/01/2017\",\"06/30/2017\",97,100)":   "0.0622012325059031",
+		"=YIELDDISC(\"01/01/2017\",\"06/30/2017\",97,100,0)": "0.0622012325059031",
+		// YIELDMAT
+		"=YIELDMAT(\"01/01/2017\",\"06/30/2018\",\"06/01/2014\",5.5%,101)":   "0.0419422478838651",
+		"=YIELDMAT(\"01/01/2017\",\"06/30/2018\",\"06/01/2014\",5.5%,101,0)": "0.0419422478838651",
 	}
 	for formula, expected := range mathCalc {
 		f := prepareCalcData(cellData)
@@ -2615,6 +2621,28 @@ func TestCalcCellValue(t *testing.T) {
 		"=SYD(10000,1000,0,1)":      "SYD requires life argument to be > 0",
 		"=SYD(10000,1000,5,0)":      "SYD requires per argument to be > 0",
 		"=SYD(10000,1000,1,5)":      "#NUM!",
+		// YIELDDISC
+		"=YIELDDISC()": "YIELDDISC requires 4 or 5 arguments",
+		"=YIELDDISC(\"\",\"06/30/2017\",97,100,0)":              "#VALUE!",
+		"=YIELDDISC(\"01/01/2017\",\"\",97,100,0)":              "#VALUE!",
+		"=YIELDDISC(\"01/01/2017\",\"06/30/2017\",\"\",100,0)":  "#VALUE!",
+		"=YIELDDISC(\"01/01/2017\",\"06/30/2017\",97,\"\",0)":   "#VALUE!",
+		"=YIELDDISC(\"01/01/2017\",\"06/30/2017\",97,100,\"\")": "#NUM!",
+		"=YIELDDISC(\"01/01/2017\",\"06/30/2017\",0,100)":       "YIELDDISC requires pr > 0",
+		"=YIELDDISC(\"01/01/2017\",\"06/30/2017\",97,0)":        "YIELDDISC requires redemption > 0",
+		"=YIELDDISC(\"01/01/2017\",\"06/30/2017\",97,100,5)":    "invalid basis",
+		// YIELDMAT
+		"=YIELDMAT()": "YIELDMAT requires 5 or 6 arguments",
+		"=YIELDMAT(\"\",\"06/30/2018\",\"06/01/2014\",5.5%,101,0)":            "#VALUE!",
+		"=YIELDMAT(\"01/01/2017\",\"\",\"06/01/2014\",5.5%,101,0)":            "#VALUE!",
+		"=YIELDMAT(\"01/01/2017\",\"06/30/2018\",\"\",5.5%,101,0)":            "#VALUE!",
+		"=YIELDMAT(\"01/01/2017\",\"06/30/2018\",\"06/01/2014\",\"\",101,0)":  "strconv.ParseFloat: parsing \"\": invalid syntax",
+		"=YIELDMAT(\"01/01/2017\",\"06/30/2018\",\"06/01/2014\",5,\"\",0)":    "strconv.ParseFloat: parsing \"\": invalid syntax",
+		"=YIELDMAT(\"01/01/2017\",\"06/30/2018\",\"06/01/2014\",5,5.5%,\"\")": "#NUM!",
+		"=YIELDMAT(\"06/01/2014\",\"06/30/2018\",\"01/01/2017\",5.5%,101,0)":  "YIELDMAT requires settlement > issue",
+		"=YIELDMAT(\"01/01/2017\",\"06/30/2018\",\"06/01/2014\",-1,101,0)":    "YIELDMAT requires rate >= 0",
+		"=YIELDMAT(\"01/01/2017\",\"06/30/2018\",\"06/01/2014\",1,0,0)":       "YIELDMAT requires pr > 0",
+		"=YIELDMAT(\"01/01/2017\",\"06/30/2018\",\"06/01/2014\",5.5%,101,5)":  "invalid basis",
 	}
 	for formula, expected := range mathCalcError {
 		f := prepareCalcData(cellData)