diff --git a/include/lsst/afw/image/PhotoCalib.h b/include/lsst/afw/image/PhotoCalib.h
index 6d5168972..7472376eb 100644
--- a/include/lsst/afw/image/PhotoCalib.h
+++ b/include/lsst/afw/image/PhotoCalib.h
@@ -389,6 +389,23 @@ class PhotoCalib final : public table::io::PersistableFacade<PhotoCalib>, public
     /// @overload magnitudeToInstFlux(double, lsst::geom::Point<double, 2> const &) const;
     double magnitudeToInstFlux(double magnitude) const;
 
+    /**
+     * Convert nanojansky to instFlux (ADU).
+     *
+     * If passed point, use the exact calculation at that point, otherwise, use the mean scaling factor.
+     *
+     * Useful for computing expected instrumental flux from reference catalog sources.
+     *
+     * @param[in]  nanojansky  The flux in nanojanksies to convert.
+     * @param[in]  point       The position that flux is to be converted at.
+     *
+     * @returns    Source instFlux in ADU.
+     */
+    double nanojanskyToInstFlux(double nanojansky, lsst::geom::Point<double, 2> const &point) const;
+
+    /// @overload nanojanskyToInstFlux(double, lsst::geom::Point<double, 2> const &) const;
+    double nanojanskyToInstFlux(double nanojansky) const;
+
     /**
      * Get the mean photometric calibration.
      *
diff --git a/python/lsst/afw/image/_photoCalib.cc b/python/lsst/afw/image/_photoCalib.cc
index 89cf09d88..d551463e9 100644
--- a/python/lsst/afw/image/_photoCalib.cc
+++ b/python/lsst/afw/image/_photoCalib.cc
@@ -154,10 +154,19 @@ void declarePhotoCalib(lsst::utils::python::WrapperCollection &wrappers) {
                 cls.def("magnitudeToInstFlux",
                         py::overload_cast<double, lsst::geom::Point<double, 2> const &>(
                                 &PhotoCalib::magnitudeToInstFlux, py::const_),
-                        "instFlux"_a, "point"_a);
+                        "magnitude"_a, "point"_a);
                 cls.def("magnitudeToInstFlux",
                         py::overload_cast<double>(&PhotoCalib::magnitudeToInstFlux, py::const_),
-                        "instFlux"_a);
+                        "magnitude"_a);
+
+                /* from nanojansky. */
+                cls.def("nanojanskyToInstFlux",
+                        py::overload_cast<double, lsst::geom::Point<double, 2> const &>(
+                                &PhotoCalib::nanojanskyToInstFlux, py::const_),
+                        "nanojansky"_a, "point"_a);
+                cls.def("nanojanskyToInstFlux",
+                        py::overload_cast<double>(&PhotoCalib::nanojanskyToInstFlux, py::const_),
+                        "nanojansky"_a);
 
                 /* utilities */
                 cls.def("getCalibrationMean", &PhotoCalib::getCalibrationMean);
diff --git a/src/image/PhotoCalib.cc b/src/image/PhotoCalib.cc
index 894872955..d9a682fb1 100644
--- a/src/image/PhotoCalib.cc
+++ b/src/image/PhotoCalib.cc
@@ -65,6 +65,8 @@ double toInstFluxFromMagnitude(double magnitude, double scale) {
     return utils::ABMagnitudeToNanojansky(magnitude) / scale;
 }
 
+double toInstFluxFromNanojansky(double nanojansky, double scale) { return nanojansky / scale; }
+
 double toNanojanskyErr(double instFlux, double instFluxErr, double scale, double scaleErr,
                        double nanojansky) {
     return std::abs(nanojansky) * hypot(instFluxErr / instFlux, scaleErr / scale);
@@ -219,6 +221,14 @@ double PhotoCalib::magnitudeToInstFlux(double magnitude, lsst::geom::Point<doubl
     return toInstFluxFromMagnitude(magnitude, evaluate(point));
 }
 
+double PhotoCalib::nanojanskyToInstFlux(double nanojansky) const {
+    return toInstFluxFromNanojansky(nanojansky, _calibrationMean);
+}
+
+double PhotoCalib::nanojanskyToInstFlux(double nanojansky, lsst::geom::Point<double, 2> const &point) const {
+    return toInstFluxFromNanojansky(nanojansky, evaluate(point));
+}
+
 std::shared_ptr<math::BoundedField> PhotoCalib::computeScaledCalibration() const {
     return *(_calibration) / _calibrationMean;
 }
diff --git a/tests/test_photoCalib.py b/tests/test_photoCalib.py
index d7fb9174f..2108b8fff 100644
--- a/tests/test_photoCalib.py
+++ b/tests/test_photoCalib.py
@@ -258,6 +258,20 @@ def _testPhotoCalibCenter(self, photoCalib, calibrationErr):
                                      photoCalib.magnitudeToInstFlux(mag2, self.pointXShift),
                                      rtol=1e-15)
 
+        # test reverse conversion: nanojansky to instFlux (no position specified)
+        self.assertFloatsAlmostEqual(self.instFlux1, photoCalib.nanojanskyToInstFlux(self.flux1))
+        self.assertFloatsAlmostEqual(self.instFlux2, photoCalib.nanojanskyToInstFlux(self.flux2), rtol=1e-15)
+
+        # test round-tripping instFlux->nanojansky->instFlux (position specified)
+        flux = photoCalib.instFluxToNanojansky(self.instFlux1, self.pointXShift)
+        self.assertFloatsAlmostEqual(self.instFlux1,
+                                     photoCalib.nanojanskyToInstFlux(flux, self.pointXShift),
+                                     rtol=1e-15)
+        flux2 = photoCalib.instFluxToNanojansky(self.instFlux2, self.pointXShift)
+        self.assertFloatsAlmostEqual(self.instFlux2,
+                                     photoCalib.nanojanskyToInstFlux(flux2, self.pointXShift),
+                                     rtol=1e-15)
+
         # test round-tripping arrays (position specified)
         instFlux1Array = np.full(10, self.instFlux1)
         instFlux2Array = np.full(10, self.instFlux2)