diff --git a/cmsdb/constants/__init__.py b/cmsdb/constants/__init__.py
index f3e670d9..235d722c 100644
--- a/cmsdb/constants/__init__.py
+++ b/cmsdb/constants/__init__.py
@@ -4,14 +4,17 @@
 Scientific constants.
 """
 
-from scinum import Number, Correlation
+from scinum import Number, Correlation, combine_uncertainties
 
 from cmsdb.util import DotDict
 
-
 # misc
 n_leps = Number(3)
 
+# Z and W branching ratios and masses from
+# https://pdg.lbl.gov/2023/tables/contents_tables.html
+# Cut-off date for Listings/Summary Tables was Jan. 15, 2023, content of the 2023 Review of Particle Physics
+
 # masses
 m_z = Number(91.1876, {"z_mass": 0.0021})
 
@@ -23,7 +26,7 @@
 br_ww = DotDict(
     fh=br_w.had ** 2,
     dl=br_w.lep ** 2,
-    sl=2 * ((br_w.had * Correlation(br_w_had=-1)) * br_w.lep),
+    sl=2 * ((br_w.had * Correlation(br_w_had=-1)) * br_w.lep),  # what does this correlation term do?
 )
 
 br_z = DotDict(
@@ -31,14 +34,41 @@
     clep=Number(0.033658, {"br_z_clep": 0.000023}) * n_leps,
 )
 
+# higgs branching ratios from lhchwg, taken for mH = 125GeV
+# https://twiki.cern.ch/twiki/bin/view/LHCPhysics/CERNYellowReportPageBR?rev=23
+
+# explanation on uncertainties and how to combine them:
+# https://cds.cern.ch/record/1416519/files/CERN-2012-002.pdf?version=1
+# section 2.1.3 : procedure to determine uncertainties
+
+
+br_h_ww_full = Number(0.2137, {"theo": (0.0099j, 0.0099j), "m_q": (0.0099j, 0.0098j), "alpha_s": (0.0066j, 0.0063j)})
+br_h_zz_full = Number(0.02619, {"theo": (0.0099j, 0.0099j), "m_q": (0.0099j, 0.0098j), "alpha_s": (0.0066j, 0.0063j)})
+br_h_gg_full = Number(0.002270, {"theo": (0.0173j, 0.0172j), "m_q": (0.0093j, 0.0099j), "alpha_s": (0.0061j, 0.0062j)})
+br_h_bb_full = Number(0.5824, {"theo": (0.0065j, 0.0065j), "m_q": (0.0072j, 0.0074j), "alpha_s": (0.0078j, 0.0080j)})
+br_h_tt_full = Number(0.06272, {"theo": (0.0117j, 0.0116j), "m_q": (0.0098j, 0.0099j), "alpha_s": (0.0062j, 0.0062j)})
+
+
+def combine_uncertainties_higgs_br(number: Number):
+    parametric_uncertainties = {
+        direction: combine_uncertainties("+", number.u("m_q", direction), number.u("alpha_s", direction), rho=0)
+        for direction in ["up", "down"]
+    }
+    return (
+        combine_uncertainties("+", number.u("theo", direction), parametric_uncertainties[direction], rho=1)
+        for direction in ["up", "down"]
+    )
+
+
 br_h = DotDict(
-    ww=Number(0.2152, {"br_h_ww": (0.0153j, 0.0152j)}),
-    zz=Number(0.02641, {"br_h_zz": (0.0153j, 0.0152j)}),
-    gg=Number(0.002270, {"br_h_gg": (0.0205j, 0.0209j)}),
-    bb=Number(0.5809, {"br_h_bb": (0.0124j, 0.0126j)}),
-    tt=Number(0.06256, {"br_h_tt": (0.0165j, 0.0163j)}),
+    ww=Number(br_h_ww_full.n, {"br_h_ww": tuple(combine_uncertainties_higgs_br(br_h_ww_full))}),
+    zz=Number(br_h_zz_full.n, {"br_h_zz": tuple(combine_uncertainties_higgs_br(br_h_zz_full))}),
+    gg=Number(br_h_gg_full.n, {"br_h_gg": tuple(combine_uncertainties_higgs_br(br_h_gg_full))}),
+    bb=Number(br_h_bb_full.n, {"br_h_bb": tuple(combine_uncertainties_higgs_br(br_h_bb_full))}),
+    tt=Number(br_h_tt_full.n, {"br_h_tt": tuple(combine_uncertainties_higgs_br(br_h_tt_full))}),
 )
 
+
 br_hh = DotDict(
     bbbb=br_h.bb ** 2,
     bbvv=2 * br_h.bb * (br_h.ww + br_h.zz),