diff --git a/CHANGES.rst b/CHANGES.rst
index bddef99e37..49ccb7e70b 100644
--- a/CHANGES.rst
+++ b/CHANGES.rst
@@ -16,6 +16,8 @@ Imviz
 - New "Catalog Search" plugin that uses a specified catalog (currently SDSS) to search for sources in an image
   and mark the sources found. [#1455]
 
+- Auto-populate simple aperture photometry values if JWST data is loaded into viewer. [#1549]
+
 Mosviz
 ^^^^^^
 - NIRISS parser now sorts FITS files by header instead of file name. [#819]
diff --git a/docs/imviz/plugins.rst b/docs/imviz/plugins.rst
index cca6143dcb..9ba4667082 100644
--- a/docs/imviz/plugins.rst
+++ b/docs/imviz/plugins.rst
@@ -149,7 +149,11 @@ an interactively selected region. A typical workflow is as follows:
    If this field is not applicable for you, leave it at 0.
    **This field resets every time Data selection changes.**
 8. If you also want photometry result in magnitude unit, you can enter a flux
-   scaling factor in the :guilabel:`Flux scaling` field. The value must be in the
+   scaling factor in the :guilabel:`Flux scaling` field.
+   :guilabel:`Flux scaling` is populated for JWST images
+   if MJy/sr data unit is detected and pixel area is given to factor out the per-steradian unit.
+   The value used, if this is the case, is the scaling to convert MJy to AB magnitude.
+   Otherwise, the value must be in the
    same unit as display data unit. A magnitude is then calculated using
    ``-2.5 * log(flux / flux_scaling)``. This calculation only makes sense if your
    display data unit is already in linear flux unit. Setting this to 1 is equivalent
diff --git a/jdaviz/configs/imviz/plugins/aper_phot_simple/aper_phot_simple.py b/jdaviz/configs/imviz/plugins/aper_phot_simple/aper_phot_simple.py
index fdc7711430..c9bf7e5d75 100644
--- a/jdaviz/configs/imviz/plugins/aper_phot_simple/aper_phot_simple.py
+++ b/jdaviz/configs/imviz/plugins/aper_phot_simple/aper_phot_simple.py
@@ -105,6 +105,9 @@ def _dataset_selected_changed(self, event={}):
             if telescope == 'JWST':
                 if 'photometry' in meta and 'pixelarea_arcsecsq' in meta['photometry']:
                     self.pixel_area = meta['photometry']['pixelarea_arcsecsq']
+                    if 'bunit_data' in meta and meta['bunit_data'] == u.Unit("MJy/sr"):
+                        # Hardcode the flux conversion factor from MJy to ABmag
+                        self.flux_scaling = 0.003631
             elif telescope == 'HST':
                 # TODO: Add more HST support, as needed.
                 # HST pixel scales are from instrument handbooks.
@@ -310,8 +313,8 @@ def vue_do_aper_phot(self, *args, **kwargs):
                 sum_ct_err = None
 
             if include_flux_scale:
-                flux_scale = flux_scale * rawsum.unit
-                sum_mag = -2.5 * np.log10(rawsum / flux_scale) * u.mag
+                flux_scale = flux_scale * phot_table['sum'][0].unit
+                sum_mag = -2.5 * np.log10(phot_table['sum'][0] / flux_scale) * u.mag
             else:
                 flux_scale = None
                 sum_mag = None
@@ -425,7 +428,7 @@ def vue_do_aper_phot(self, *args, **kwargs):
                 x = phot_table[key][0]
                 if (isinstance(x, (int, float, u.Quantity)) and
                         key not in ('xcentroid', 'ycentroid', 'sky_centroid', 'sum_aper_area',
-                                    'aperture_sum_counts')):
+                                    'aperture_sum_counts', 'aperture_sum_mag')):
                     tmp.append({'function': key, 'result': f'{x:.4e}'})
                 elif key == 'sky_centroid' and x is not None:
                     tmp.append({'function': 'RA centroid', 'result': f'{x.ra.deg:.4f} deg'})
@@ -435,6 +438,8 @@ def vue_do_aper_phot(self, *args, **kwargs):
                 elif key == 'aperture_sum_counts' and x is not None:
                     tmp.append({'function': key, 'result':
                                 f'{x:.4e} ({phot_table["aperture_sum_counts_err"][0]:.4e})'})
+                elif key == 'aperture_sum_mag' and x is not None:
+                    tmp.append({'function': key, 'result': f'{x:.3f}'})
                 else:
                     tmp.append({'function': key, 'result': str(x)})
 
diff --git a/jdaviz/configs/imviz/tests/test_parser.py b/jdaviz/configs/imviz/tests/test_parser.py
index c500d996ef..539fdc6407 100644
--- a/jdaviz/configs/imviz/tests/test_parser.py
+++ b/jdaviz/configs/imviz/tests/test_parser.py
@@ -270,7 +270,7 @@ def test_parse_jwst_nircam_level2(self, imviz_helper):
         phot_plugin.counts_factor = (data.meta['photometry']['conversion_megajanskys'] /
                                      data.meta['exposure']['exposure_time'])
         assert_allclose(phot_plugin.counts_factor, 0.0036385915646798953)
-        phot_plugin.flux_scaling = 1  # Simple mag, no zeropoint
+        assert_allclose(phot_plugin.flux_scaling, 0.003631)
         phot_plugin.vue_do_aper_phot()
         tbl = imviz_helper.get_aperture_photometry_results()
         assert_quantity_allclose(tbl[0]['xcentroid'], 970.935492 * u.pix)
@@ -286,8 +286,8 @@ def test_parse_jwst_nircam_level2(self, imviz_helper):
         assert_quantity_allclose(tbl[0]['aperture_sum_counts'], 132061.576643 * u.count, rtol=1e-6)
         assert_quantity_allclose(tbl[0]['aperture_sum_counts_err'], 363.402775 * u.count)
         assert_quantity_allclose(tbl[0]['counts_fac'], 0.0036385915646798953 * (data_unit / u.ct))
-        assert_quantity_allclose(tbl[0]['aperture_sum_mag'], -6.704274 * u.mag)
-        assert_quantity_allclose(tbl[0]['flux_scaling'], 1 * data_unit)
+        assert_quantity_allclose(tbl[0]['aperture_sum_mag'], 19.770299 * u.mag)
+        assert_quantity_allclose(tbl[0]['flux_scaling'], 3631 * u.Jy)
         assert_quantity_allclose(tbl[0]['min'], 0.041017 * data_unit, atol=1e-5 * data_unit)
         assert_quantity_allclose(tbl[0]['max'], 138.923752 * data_unit, rtol=1e-5)
         assert_quantity_allclose(tbl[0]['mean'], 4.391718 * data_unit)