diff --git a/Software/PC_Application/Calibration/calibration.cpp b/Software/PC_Application/Calibration/calibration.cpp
index 8a6738e..75d460d 100644
--- a/Software/PC_Application/Calibration/calibration.cpp
+++ b/Software/PC_Application/Calibration/calibration.cpp
@@ -27,6 +27,7 @@ Calibration::Calibration()
 
     type = Type::None;
     port1Standard = port2Standard = PortStandard::Male;
+    throughZeroLength = false;
 }
 
 Calibration::Standard Calibration::getPort1Standard(Calibration::Measurement m)
@@ -141,6 +142,10 @@ bool Calibration::constructErrorTerms(Calibration::Type type)
         port1Standard = PortStandard::Male;
         port2Standard = PortStandard::Male;
     }
+    if(port1Standard == port2Standard) {
+        // unable to use zero-length through
+        throughZeroLength = false;
+    }
     switch(type) {
     case Type::Port1SOL: constructPort1SOL(); break;
     case Type::Port2SOL: constructPort2SOL(); break;
@@ -194,6 +199,14 @@ void Calibration::construct12TermPoints()
         p.fe30 = S21_isolation;
         // See page 18 of https://www.rfmentor.com/sites/default/files/NA_Error_Models_and_Cal_Methods.pdf
         // Formulas for S11M and S21M solved for e22 and e10e32
+        if (throughZeroLength) {
+            // use ideal through
+            actual.ThroughS11 = 0.0;
+            actual.ThroughS12 = 1.0;
+            actual.ThroughS21 = 1.0;
+            actual.ThroughS22 = 0.0;
+        }
+
         auto deltaS = actual.ThroughS11*actual.ThroughS22 - actual.ThroughS21 * actual.ThroughS12;
         p.fe22 = ((S11_through - p.fe00)*(1.0 - p.fe11 * actual.ThroughS11)-actual.ThroughS11*p.fe10e01)
                 / ((S11_through - p.fe00)*(actual.ThroughS22-p.fe11*deltaS)-deltaS*p.fe10e01);
@@ -859,6 +872,16 @@ QString Calibration::descriptiveCalName(){
     return tmp;
 }
 
+bool Calibration::getThroughZeroLength() const
+{
+    return throughZeroLength;
+}
+
+void Calibration::setThroughZeroLength(bool value)
+{
+    throughZeroLength = value;
+}
+
 double Calibration::getMinFreq(){
     return this->minFreq;
 }
@@ -900,6 +923,7 @@ nlohmann::json Calibration::toJSON()
     j["type"] = TypeToString(getType()).toStdString();
     j["port1StandardMale"] = port1Standard == PortStandard::Male;
     j["port2StandardMale"] = port2Standard == PortStandard::Male;
+    j["throughZeroLength"] = throughZeroLength;
 
     return j;
 }
@@ -910,6 +934,7 @@ void Calibration::fromJSON(nlohmann::json j)
     resetErrorTerms();
     port1Standard = j.value("port1StandardMale", true) ? PortStandard::Male : PortStandard::Female;
     port2Standard = j.value("port2StandardMale", true) ? PortStandard::Male : PortStandard::Female;
+    throughZeroLength = j.value("throughZeroLength", false);
     if(j.contains("measurements")) {
         // grab measurements
         for(auto j_m : j["measurements"]) {
@@ -981,6 +1006,11 @@ ostream& operator<<(ostream &os, const Calibration &c)
 
 istream& operator >>(istream &in, Calibration &c)
 {
+    // old file format did not contain port standard gender, set default
+    c.port1Standard = Calibration::PortStandard::Male;
+    c.port2Standard = Calibration::PortStandard::Male;
+    c.throughZeroLength = false;
+
     std::string line;
     while(getline(in, line)) {
         QString qLine = QString::fromStdString(line).simplified();
@@ -1020,9 +1050,6 @@ istream& operator >>(istream &in, Calibration &c)
             }
         }
     }
-    // old file format did not contain port standard gender, set default
-    c.port1Standard = Calibration::PortStandard::Male;
-    c.port2Standard = Calibration::PortStandard::Male;
     qDebug() << "Calibration file parsing complete";
     return in;
 }
diff --git a/Software/PC_Application/Calibration/calibration.h b/Software/PC_Application/Calibration/calibration.h
index f465790..f3f2717 100644
--- a/Software/PC_Application/Calibration/calibration.h
+++ b/Software/PC_Application/Calibration/calibration.h
@@ -115,6 +115,8 @@ public:
     };
     void setPortStandard(int port, PortStandard standard);
     PortStandard getPortStandard(int port);
+    bool getThroughZeroLength() const;
+    void setThroughZeroLength(bool value);
 
     QString getCurrentCalibrationFile();
     double getMinFreq();
@@ -176,6 +178,7 @@ private:
     QString currentCalFile;
 
     PortStandard port1Standard, port2Standard;
+    bool throughZeroLength;
 };
 
 #endif // CALIBRATION_H
diff --git a/Software/PC_Application/Calibration/calibrationtracedialog.cpp b/Software/PC_Application/Calibration/calibrationtracedialog.cpp
index 74f8775..55c2f08 100644
--- a/Software/PC_Application/Calibration/calibrationtracedialog.cpp
+++ b/Software/PC_Application/Calibration/calibrationtracedialog.cpp
@@ -26,12 +26,26 @@ CalibrationTraceDialog::CalibrationTraceDialog(Calibration *cal, double f_min, d
     ui->tableView->setColumnWidth(3, 160);
     UpdateCalibrationStatus();
 
+    auto updateThroughStandardUI = [=](){
+        if(cal->getPortStandard(1) == cal->getPortStandard(2)) {
+            // same gender on both ports, can't use zero length through
+            ui->throughCalkit->click();
+            ui->throughZero->setEnabled(false);
+            ui->throughCalkit->setEnabled(false);
+        } else {
+            // user may select option for through
+            ui->throughZero->setEnabled(true);
+            ui->throughCalkit->setEnabled(true);
+        }
+    };
+
     connect(ui->port1Group, qOverload<int>(&QButtonGroup::buttonClicked), [=](){
         if(ui->port1Male->isChecked()) {
             cal->setPortStandard(1, Calibration::PortStandard::Male);
         } else {
             cal->setPortStandard(1, Calibration::PortStandard::Female);
         }
+        updateThroughStandardUI();
         UpdateCalibrationStatus();
     });
 
@@ -41,6 +55,16 @@ CalibrationTraceDialog::CalibrationTraceDialog(Calibration *cal, double f_min, d
         } else {
             cal->setPortStandard(2, Calibration::PortStandard::Female);
         }
+        updateThroughStandardUI();
+        UpdateCalibrationStatus();
+    });
+
+    connect(ui->throughGroup, qOverload<int>(&QButtonGroup::buttonClicked), [=](){
+        if(ui->throughZero->isChecked()) {
+            cal->setThroughZeroLength(true);
+        } else {
+            cal->setThroughZeroLength(false);
+        }
         UpdateCalibrationStatus();
     });
 
@@ -48,9 +72,11 @@ CalibrationTraceDialog::CalibrationTraceDialog(Calibration *cal, double f_min, d
     if(!cal->getCalibrationKit().hasSeparateMaleFemaleStandards()) {
         ui->port1Standards->hide();
         ui->port2Standards->hide();
+        ui->throughStandard->hide();
         // default selection is male
         ui->port1Male->click();
         ui->port2Male->click();
+        ui->throughCalkit->click();
     } else {
         // separate standards defined
         if(cal->getPortStandard(1) == Calibration::PortStandard::Male) {
@@ -63,6 +89,12 @@ CalibrationTraceDialog::CalibrationTraceDialog(Calibration *cal, double f_min, d
         } else {
             ui->port2Female->setChecked(true);
         }
+        if(cal->getThroughZeroLength()) {
+            ui->throughZero->setChecked(true);
+        } else {
+            ui->throughCalkit->setChecked(true);
+        }
+        updateThroughStandardUI();
     }
 
     // Check calibration kit span
diff --git a/Software/PC_Application/Calibration/calibrationtracedialog.ui b/Software/PC_Application/Calibration/calibrationtracedialog.ui
index 0a4dea5..58dd531 100644
--- a/Software/PC_Application/Calibration/calibrationtracedialog.ui
+++ b/Software/PC_Application/Calibration/calibrationtracedialog.ui
@@ -18,7 +18,7 @@
   </property>
   <layout class="QVBoxLayout" name="verticalLayout">
    <item>
-    <layout class="QHBoxLayout" name="horizontalLayout_4">
+    <layout class="QHBoxLayout" name="horizontalLayout_5">
      <item>
       <widget class="QGroupBox" name="port1Standards">
        <property name="title">
@@ -77,6 +77,35 @@
        </layout>
       </widget>
      </item>
+     <item>
+      <widget class="QGroupBox" name="throughStandard">
+       <property name="title">
+        <string>Through Standard</string>
+       </property>
+       <layout class="QHBoxLayout" name="horizontalLayout_4">
+        <item>
+         <widget class="QRadioButton" name="throughCalkit">
+          <property name="text">
+           <string>From calibration kit</string>
+          </property>
+          <attribute name="buttonGroup">
+           <string notr="true">throughGroup</string>
+          </attribute>
+         </widget>
+        </item>
+        <item>
+         <widget class="QRadioButton" name="throughZero">
+          <property name="text">
+           <string>Zero-length through</string>
+          </property>
+          <attribute name="buttonGroup">
+           <string notr="true">throughGroup</string>
+          </attribute>
+         </widget>
+        </item>
+       </layout>
+      </widget>
+     </item>
      <item>
       <spacer name="horizontalSpacer_2">
        <property name="orientation">
@@ -173,5 +202,6 @@
  <buttongroups>
   <buttongroup name="port1Group"/>
   <buttongroup name="port2Group"/>
+  <buttongroup name="throughGroup"/>
  </buttongroups>
 </ui>