diff --git a/README.md b/README.md
index 7674f2e..a8a2b76 100644
--- a/README.md
+++ b/README.md
@@ -112,8 +112,8 @@ local opts = {
 require('deadcolumn').setup(opts) -- Call the setup function
 ```
 
-- `scope` (string): The scope for showing the colored column, there are several
-  possible values:
+- `scope` (string|function): The scope for showing the colored column, there
+  are several possible values:
 
     - `'line'`: colored column will be shown based on the length of the current
       line.
@@ -127,6 +127,24 @@ require('deadcolumn').setup(opts) -- Call the setup function
     - `'cursor'`: colored column will be shown based on current cursor
       position.
 
+    - function() -> number: callback function that returns a number as the
+      length of the row. For example, to show the colored column based on the
+      longest line in the nearby 100 lines:
+
+      ```lua
+        require('deadcolumn').setup({
+        scope = function()
+            local max = 0
+            for i = -50, 50 do
+            local len = vim.fn.strdisplaywidth(vim.fn.getline(vim.fn.line('.') + i))
+            if len > max then
+                max = len
+            end
+            return max
+        end
+        })
+      ```
+
 - `modes` (table): In which modes to show the colored column.
 
 - `blending` (table): Blending options.
diff --git a/doc/deadcolumn.nvim.txt b/doc/deadcolumn.nvim.txt
index c3370b3..e0b831a 100644
--- a/doc/deadcolumn.nvim.txt
+++ b/doc/deadcolumn.nvim.txt
@@ -74,7 +74,7 @@ deadcolumn.setup({*opts})                         *deadcolumn.options.setup()*
     Valid keys for {opts}
 
                                                *deadcolumn.options.opts.scope*
-    `scope` string (default "line")
+    `scope` string|function (default "line")
 
 	The scope for showing the colored column.
 
@@ -99,6 +99,26 @@ deadcolumn.setup({*opts})                         *deadcolumn.options.setup()*
 
 	    Colored column will be shown based on current cursor position.
 
+	5. function() -> number
+
+	    Callback function that returns a number as the length of the
+	    row. For example, to show the colored column based on the longest
+            line in the nearby 100 lines: >lua
+
+	    require('deadcolumn').setup({
+		scope = function()
+		    local max = 0
+		    for i = -50, 50 do
+			local len = vim.fn.strdisplaywidth(vim.fn.getline(vim.fn.line('.') + i))
+			if len > max then
+			    max = len
+			end
+		    end
+		    return max
+		end
+	    })
+<
+
                                                 *deadcolumn.options.ops.modes*
     `modes` table
 	(default: { "i", "ic", "ix", "R", "Rc", "Rx", "Rv", "Rvc", "Rvx" })
diff --git a/lua/deadcolumn/autocmds.lua b/lua/deadcolumn/autocmds.lua
index f7e7931..ef806a4 100644
--- a/lua/deadcolumn/autocmds.lua
+++ b/lua/deadcolumn/autocmds.lua
@@ -97,7 +97,9 @@ local function redraw_cc()
     return
   end
 
-  local len = scope_len_fn[configs.opts.scope]()
+  local len = type(configs.opts.scope) == 'string'
+      and scope_len_fn[configs.opts.scope]()
+    or configs.opts.scope()
   local thresh = configs.opts.blending.threshold
   if 0 < thresh and thresh <= 1 then
     thresh = math.floor(thresh * cc)
diff --git a/lua/deadcolumn/configs.lua b/lua/deadcolumn/configs.lua
index 26b970b..c5e0f89 100644
--- a/lua/deadcolumn/configs.lua
+++ b/lua/deadcolumn/configs.lua
@@ -33,8 +33,12 @@ function M.set_options(user_opts)
   end
   assert(vim.tbl_islist(M.opts.modes), 'modes must be a list of strings')
   assert(
-    vim.tbl_contains({ 'line', 'buffer', 'visible', 'cursor' }, M.opts.scope),
-    'scope must be one of "line", "buffer", "visible", "cursor"'
+    type(M.opts.scope) == 'function'
+      or vim.tbl_contains(
+        { 'line', 'buffer', 'visible', 'cursor' },
+        M.opts.scope
+      ),
+    'scope must be a function or one of "line", "buffer", "visible", "cursor"'
   )
   assert(M.opts.blending.threshold >= 0, 'blending.threshold must be >= 0')
   assert(