diff --git a/docs/CHANGELOG.txt b/docs/CHANGELOG.txt
index b93888c85..6650debf0 100644
--- a/docs/CHANGELOG.txt
+++ b/docs/CHANGELOG.txt
@@ -62,6 +62,8 @@ Other changes:
 - Tools: binary_to_compressed_c: added -u8/-u32/-base85 export options.
 - Demo: example tree used by Property Editor & Selection demos properly freed
   on application closure. (#8158) [@Legulysse]
+- Fonts: fixed AddCustomRect() not being packed with TexGlyphPadding + not accounted
+  for surface area used to determine best-guess texture size. (#8107) [@YarikTH, @ocornut]
 - Misc: use SSE 4.2 crc32 instructions when available. (#8169, #4933) [@Teselka]
 - Backends: Vulkan: Make user-provided descriptor pool optional. As a convenience,
   when setting init_info->DescriptorPoolSize then the backend will create and manage
diff --git a/imgui.h b/imgui.h
index 30115e810..423e2a8ba 100644
--- a/imgui.h
+++ b/imgui.h
@@ -3230,8 +3230,8 @@ struct ImFontConfig
     float           SizePixels;             //          // Size in pixels for rasterizer (more or less maps to the resulting font height).
     int             OversampleH;            // 2        // Rasterize at higher quality for sub-pixel positioning. Note the difference between 2 and 3 is minimal. You can reduce this to 1 for large glyphs save memory. Read https://github.com/nothings/stb/blob/master/tests/oversample/README.md for details.
     int             OversampleV;            // 1        // Rasterize at higher quality for sub-pixel positioning. This is not really useful as we don't use sub-pixel positions on the Y axis.
-    bool            PixelSnapH;             // false    // Align every glyph to pixel boundary. Useful e.g. if you are merging a non-pixel aligned font with the default font. If enabled, you can set OversampleH/V to 1.
-    ImVec2          GlyphExtraSpacing;      // 0, 0     // Extra spacing (in pixels) between glyphs. Only X axis is supported for now.
+    bool            PixelSnapH;             // false    // Align every glyph AdvanceX to pixel boundaries. Useful e.g. if you are merging a non-pixel aligned font with the default font. If enabled, you can set OversampleH/V to 1.
+    ImVec2          GlyphExtraSpacing;      // 0, 0     // Extra spacing (in pixels) between glyphs when rendered: essentially add to glyph->AdvanceX. Only X axis is supported for now.
     ImVec2          GlyphOffset;            // 0, 0     // Offset all glyphs from this font input.
     const ImWchar*  GlyphRanges;            // NULL     // THE ARRAY DATA NEEDS TO PERSIST AS LONG AS THE FONT IS ALIVE. Pointer to a user-provided list of Unicode range (2 value per range, values are inclusive, zero-terminated list).
     float           GlyphMinAdvanceX;       // 0        // Minimum AdvanceX for glyphs, set Min to align font icons, set both Min/Max to enforce mono-space font
@@ -3389,7 +3389,7 @@ struct ImFontAtlas
     ImFontAtlasFlags            Flags;              // Build flags (see ImFontAtlasFlags_)
     ImTextureID                 TexID;              // User data to refer to the texture once it has been uploaded to user's graphic systems. It is passed back to you during rendering via the ImDrawCmd structure.
     int                         TexDesiredWidth;    // Texture width desired by user before Build(). Must be a power-of-two. If have many glyphs your graphics API have texture size restrictions you may want to increase texture width to decrease height.
-    int                         TexGlyphPadding;    // Padding between glyphs within texture in pixels. Defaults to 1. If your rendering method doesn't rely on bilinear filtering you may set this to 0 (will also need to set AntiAliasedLinesUseTex = false).
+    int                         TexGlyphPadding;    // FIXME: Should be called "TexPackPadding". Padding between glyphs within texture in pixels. Defaults to 1. If your rendering method doesn't rely on bilinear filtering you may set this to 0 (will also need to set AntiAliasedLinesUseTex = false).
     bool                        Locked;             // Marked as Locked by ImGui::NewFrame() so attempt to modify the atlas will assert.
     void*                       UserData;           // Store your own atlas related user-data (if e.g. you have multiple font atlas).
 
diff --git a/imgui_draw.cpp b/imgui_draw.cpp
index fd1feb0a8..631472a71 100644
--- a/imgui_draw.cpp
+++ b/imgui_draw.cpp
@@ -2941,6 +2941,7 @@ static bool ImFontAtlasBuildWithStbTruetype(ImFontAtlas* atlas)
     int total_surface = 0;
     int buf_rects_out_n = 0;
     int buf_packedchars_out_n = 0;
+    const int pack_padding = atlas->TexGlyphPadding;
     for (int src_i = 0; src_i < src_tmp_array.Size; src_i++)
     {
         ImFontBuildSrcData& src_tmp = src_tmp_array[src_i];
@@ -2964,18 +2965,19 @@ static bool ImFontAtlasBuildWithStbTruetype(ImFontAtlas* atlas)
 
         // Gather the sizes of all rectangles we will need to pack (this loop is based on stbtt_PackFontRangesGatherRects)
         const float scale = (cfg.SizePixels > 0.0f) ? stbtt_ScaleForPixelHeight(&src_tmp.FontInfo, cfg.SizePixels * cfg.RasterizerDensity) : stbtt_ScaleForMappingEmToPixels(&src_tmp.FontInfo, -cfg.SizePixels * cfg.RasterizerDensity);
-        const int padding = atlas->TexGlyphPadding;
         for (int glyph_i = 0; glyph_i < src_tmp.GlyphsList.Size; glyph_i++)
         {
             int x0, y0, x1, y1;
             const int glyph_index_in_font = stbtt_FindGlyphIndex(&src_tmp.FontInfo, src_tmp.GlyphsList[glyph_i]);
             IM_ASSERT(glyph_index_in_font != 0);
             stbtt_GetGlyphBitmapBoxSubpixel(&src_tmp.FontInfo, glyph_index_in_font, scale * cfg.OversampleH, scale * cfg.OversampleV, 0, 0, &x0, &y0, &x1, &y1);
-            src_tmp.Rects[glyph_i].w = (stbrp_coord)(x1 - x0 + padding + cfg.OversampleH - 1);
-            src_tmp.Rects[glyph_i].h = (stbrp_coord)(y1 - y0 + padding + cfg.OversampleV - 1);
+            src_tmp.Rects[glyph_i].w = (stbrp_coord)(x1 - x0 + pack_padding + cfg.OversampleH - 1);
+            src_tmp.Rects[glyph_i].h = (stbrp_coord)(y1 - y0 + pack_padding + cfg.OversampleV - 1);
             total_surface += src_tmp.Rects[glyph_i].w * src_tmp.Rects[glyph_i].h;
         }
     }
+    for (int i = 0; i < atlas->CustomRects.Size; i++)
+        total_surface += (atlas->CustomRects[i].Width + pack_padding) * (atlas->CustomRects[i].Height + pack_padding);
 
     // We need a width for the skyline algorithm, any width!
     // The exact width doesn't really matter much, but some API/GPU have texture size limitations and increasing width can decrease height.
@@ -2991,7 +2993,8 @@ static bool ImFontAtlasBuildWithStbTruetype(ImFontAtlas* atlas)
     // Pack our extra data rectangles first, so it will be on the upper-left corner of our texture (UV will have small values).
     const int TEX_HEIGHT_MAX = 1024 * 32;
     stbtt_pack_context spc = {};
-    stbtt_PackBegin(&spc, NULL, atlas->TexWidth, TEX_HEIGHT_MAX, 0, atlas->TexGlyphPadding, NULL);
+    stbtt_PackBegin(&spc, NULL, atlas->TexWidth, TEX_HEIGHT_MAX, 0, 0, NULL);
+    spc.padding = atlas->TexGlyphPadding; // Because we mixup stbtt_PackXXX and stbrp_PackXXX there's a bit of a hack here, not passing the value to stbtt_PackBegin() allows us to still pack a TexWidth-1 wide item. (#8107)
     ImFontAtlasBuildPackCustomRects(atlas, spc.pack_info);
 
     // 6. Pack each source font. No rendering yet, we are working with rectangles in an infinitely tall texture at this point.
@@ -3137,13 +3140,14 @@ void ImFontAtlasBuildPackCustomRects(ImFontAtlas* atlas, void* stbrp_context_opa
     if (user_rects.Size < 1) { __builtin_unreachable(); } // Workaround for GCC bug if IM_ASSERT() is defined to conditionally throw (see #5343)
 #endif
 
+    const int pack_padding = atlas->TexGlyphPadding;
     ImVector<stbrp_rect> pack_rects;
     pack_rects.resize(user_rects.Size);
     memset(pack_rects.Data, 0, (size_t)pack_rects.size_in_bytes());
     for (int i = 0; i < user_rects.Size; i++)
     {
-        pack_rects[i].w = user_rects[i].Width;
-        pack_rects[i].h = user_rects[i].Height;
+        pack_rects[i].w = user_rects[i].Width + pack_padding;
+        pack_rects[i].h = user_rects[i].Height + pack_padding;
     }
     stbrp_pack_rects(pack_context, &pack_rects[0], pack_rects.Size);
     for (int i = 0; i < pack_rects.Size; i++)
@@ -3151,7 +3155,7 @@ void ImFontAtlasBuildPackCustomRects(ImFontAtlas* atlas, void* stbrp_context_opa
         {
             user_rects[i].X = (unsigned short)pack_rects[i].x;
             user_rects[i].Y = (unsigned short)pack_rects[i].y;
-            IM_ASSERT(pack_rects[i].w == user_rects[i].Width && pack_rects[i].h == user_rects[i].Height);
+            IM_ASSERT(pack_rects[i].w == user_rects[i].Width + pack_padding && pack_rects[i].h == user_rects[i].Height + pack_padding);
             atlas->TexHeight = ImMax(atlas->TexHeight, pack_rects[i].y + pack_rects[i].h);
         }
 }
diff --git a/misc/freetype/imgui_freetype.cpp b/misc/freetype/imgui_freetype.cpp
index e68a2af40..bee15ba08 100644
--- a/misc/freetype/imgui_freetype.cpp
+++ b/misc/freetype/imgui_freetype.cpp
@@ -573,6 +573,7 @@ bool ImFontAtlasBuildWithFreeTypeEx(FT_Library ft_library, ImFontAtlas* atlas, u
     // 8. Render/rasterize font characters into the texture
     int total_surface = 0;
     int buf_rects_out_n = 0;
+    const int pack_padding = atlas->TexGlyphPadding;
     for (int src_i = 0; src_i < src_tmp_array.Size; src_i++)
     {
         ImFontBuildSrcDataFT& src_tmp = src_tmp_array[src_i];
@@ -590,7 +591,6 @@ bool ImFontAtlasBuildWithFreeTypeEx(FT_Library ft_library, ImFontAtlas* atlas, u
             ImFontAtlasBuildMultiplyCalcLookupTable(multiply_table, cfg.RasterizerMultiply);
 
         // Gather the sizes of all rectangles we will need to pack
-        const int padding = atlas->TexGlyphPadding;
         for (int glyph_i = 0; glyph_i < src_tmp.GlyphsList.Size; glyph_i++)
         {
             ImFontBuildSrcGlyphFT& src_glyph = src_tmp.GlyphsList[glyph_i];
@@ -623,6 +623,8 @@ bool ImFontAtlasBuildWithFreeTypeEx(FT_Library ft_library, ImFontAtlas* atlas, u
             total_surface += src_tmp.Rects[glyph_i].w * src_tmp.Rects[glyph_i].h;
         }
     }
+    for (int i = 0; i < atlas->CustomRects.Size; i++)
+        total_surface += (atlas->CustomRects[i].Width + pack_padding) * (atlas->CustomRects[i].Height + pack_padding);
 
     // We need a width for the skyline algorithm, any width!
     // The exact width doesn't really matter much, but some API/GPU have texture size limitations and increasing width can decrease height.