diff --git a/lib/awful/screen.lua b/lib/awful/screen.lua
index c6c88f73a..914875188 100644
--- a/lib/awful/screen.lua
+++ b/lib/awful/screen.lua
@@ -504,6 +504,40 @@ function screen.object.get_selected_tag(s)
     return screen.object.get_selected_tags(s)[1]
 end
 
+--- The number of pixels per inch of the screen.
+-- @property dpi
+-- @treturn number the DPI value.
+
+local xft_dpi, fallback_dpi
+
+function screen.object.get_dpi(s)
+    local mm_per_inch = 25.4
+
+    if s.data.dpi then
+        return s.data.dpi
+    end
+
+    -- Xft.dpi is explicit user configuration, so honor it
+    if not xft_dpi and awesome and awesome.xrdb_get_value then
+        xft_dpi = tonumber(awesome.xrdb_get_value("", "Xft.dpi")) or false
+    end
+    if xft_dpi then
+        return xft_dpi
+    end
+
+    -- We have no outputs, so guess based on the size of the root window.
+    if root and not fallback_dpi then
+        local _, h = root.size()
+        local _, hmm = root.size_mm()
+        fallback_dpi = hmm ~= 0 and h * mm_per_inch / hmm
+    end
+    return fallback_dpi or 96
+end
+
+function screen.object.set_dpi(s, dpi)
+    s.data.dpi = dpi
+end
+
 
 --- When the tag history changed.
 -- @signal tag::history::update
diff --git a/lib/awful/widget/calendar_popup.lua b/lib/awful/widget/calendar_popup.lua
index b3afe3026..da5cefabb 100644
--- a/lib/awful/widget/calendar_popup.lua
+++ b/lib/awful/widget/calendar_popup.lua
@@ -173,7 +173,7 @@ local function get_geometry(widget, screen, position)
     local pos, s = position or "cc", screen or ascreen.focused()
     local margin = widget._calendar_margin or 0
     local wa = s.workarea
-    local width, height = widget:fit({screen=s, dpi=beautiful.xresources.get_dpi(s)}, wa.width, wa.height)
+    local width, height = widget:fit({screen=s, dpi=s.dpi}, wa.width, wa.height)
 
     width  = width  < wa.width  and width  or wa.width
     height = height < wa.height and height or wa.height
diff --git a/lib/beautiful/xresources.lua b/lib/beautiful/xresources.lua
index ce6e78eac..fae96b167 100644
--- a/lib/beautiful/xresources.lua
+++ b/lib/beautiful/xresources.lua
@@ -64,8 +64,6 @@ function xresources.get_current_theme()
 end
 
 
-local dpi_per_screen = {}
-
 local function get_screen(s)
     return s and screen[s]
 end
@@ -75,8 +73,8 @@ end
 -- @treturn number DPI value.
 function xresources.get_dpi(s)
     s = get_screen(s)
-    if dpi_per_screen[s] then
-        return dpi_per_screen[s]
+    if s then
+        return s.dpi
     end
     if not xresources.dpi then
         -- Might not be present when run under unit tests
@@ -115,7 +113,7 @@ function xresources.set_dpi(dpi, s)
     if not s then
         xresources.dpi = dpi
     else
-        dpi_per_screen[s] = dpi
+        s.dpi = dpi
     end
 end
 
diff --git a/lib/wibox/drawable.lua b/lib/wibox/drawable.lua
index e3e3eb502..cf9a129e7 100644
--- a/lib/wibox/drawable.lua
+++ b/lib/wibox/drawable.lua
@@ -44,7 +44,7 @@ local function get_widget_context(self)
     end
 
     local context = self._widget_context
-    local dpi = beautiful.xresources.get_dpi(s)
+    local dpi = s.dpi
     if (not context) or context.screen ~= s or context.dpi ~= dpi then
         context = {
             screen = s,
diff --git a/lib/wibox/widget/textbox.lua b/lib/wibox/widget/textbox.lua
index 87039d889..628dccd81 100644
--- a/lib/wibox/widget/textbox.lua
+++ b/lib/wibox/widget/textbox.lua
@@ -73,7 +73,7 @@ end
 -- @treturn number The preferred width.
 -- @treturn number The preferred height.
 function textbox:get_preferred_size(s)
-    return self:get_preferred_size_at_dpi(beautiful.xresources.get_dpi(s))
+    return self:get_preferred_size_at_dpi(screen[s].dpi)
 end
 
 --- Get the preferred height of a textbox at a given width.
@@ -83,7 +83,7 @@ end
 -- @tparam integer|screen s The screen on which the textbox will be displayed.
 -- @treturn number The needed height.
 function textbox:get_height_for_width(width, s)
-    return self:get_height_for_width_at_dpi(width, beautiful.xresources.get_dpi(s))
+    return self:get_height_for_width_at_dpi(width, screen[s].dpi)
 end
 
 --- Get the preferred size of a textbox.