Sprite Sheet Frame Size — Measure Cell, Margin and Spacing
Phaser, Godot, Unity and Defold all ask the same four questions before they cut a sheet: how wide one frame is, how tall, how far the first frame sits from the edge, and how many pixels lie between frames. The Sprite workspace measures those numbers from the pixels and shows them with a confidence, so you stop trying 32, then 48, then 64.
- Godot 4Verified· Godot 4.7.2
- Unity 6Verified· Unity 6000.5.3f1
- Phaser 3 / 4Verified· Phaser 3.90 + 4.2
- PixiJS 8Verified· PixiJS 8.21
- Aseprite JSONVerified· Phaser load.aseprite · PixiJS 8.21
- .asepriteVerified· Aseprite 1.3.18
- Spine / libGDXVerified· spine-canvas 4.2
- Starling / Sparrow XMLVerified· Phaser 4.2
- LÖVEVerified· LÖVE 11.5
- DefoldBuilt· Defold bob.jar 1.13.1
- GameMakerUNVERIFIED
- CSS spritesVerified· Chromium
- GIF / APNGDecoded· Pillow
What it does
- Cell size, margin and spacing are measured from the pixels — transparent separator lines, the repeat pitch of the art, content crossing a cell edge — and each candidate grid carries a high, medium or low confidence with its reasons.
- The best grid is drawn over the sheet as a preview; nothing is cut until Apply, and another candidate is one click away.
- For a sheet no measurement can read, the custom grid takes cell width and height, offset X/Y (the margin) and gap X/Y (the spacing) — the same four numbers engines ask for.
- Uneven sheets can be cut by islands instead of a grid; such a sheet has no single frame size, and an atlas export is the way into the engine.
- Or skip the typing: Pack & Export writes atlas data with every frame's exact rectangle, which Godot 4.7.2, Unity 6 and Phaser 3.90 / 4.2 loaded in the verification runs.
How to do it
- Drop the sheet on the Sprite workspace.
- Read the grid decision in the Import panel: cell size, offset and gap, with the confidence.
- If it is off, choose an alternative or type the custom grid, then press Apply.
- Copy the numbers into your engine using the table below, or open Pack & Export and export for that engine.
Where the measured numbers go
| Engine | Field names | Measured value to enter |
|---|---|---|
| Phaser 3 / 4 · this.load.spritesheet | frameWidth, frameHeight, margin, spacing | Cell width, cell height, offset (one value), gap (one value) |
| Godot 4 · Sprite2D | hframes, vframes | Columns and rows — only when offset and gap are both 0 |
| Godot 4 · SpriteFrames | An AtlasTexture region per frame | Written for you by the Godot 4 export (verified in 4.7.2) |
| Unity · Sprite Editor › Slice › Grid By Cell Size | Pixel Size, Offset, Padding | Cell size, offset X/Y, gap X/Y |
| Defold · tile source | tile_width, tile_height, tile_margin, tile_spacing | Cell size; the Studio's .tilesource re-lays the frames with margin and spacing 0 (built with bob.jar 1.13.1) |
Field names are the engines' own. We did not run these hand-typed settings in the engines; the checked route is exporting an atlas from Pack & Export.
Engine exports and how each was checked
"Verified" means the exported files were loaded by the real engine or tool on real CC0 assets and the result was compared with the source. Anything that was not loaded is labelled as such.
| Target | Files | Check |
|---|---|---|
| Godot 4 | .tres SpriteFrames · .tscn AnimatedSprite2D · .png.import | Verified Godot 4.7.2Loaded by Godot; every animation frame drawn and compared with the source file. The scene uses Nearest filtering; rotation is never used. |
| Unity 6 | .unity.json · Editor/NerulioSpriteImporter.cs · AnimationClip | Verified Unity 6000.5.3f1Batch mode: sprite rects, pivots, pixels, clip keys and durations checked. |
| Phaser 3 / 4 | atlas JSON (multiatlas) · .anims.json | Verified Phaser 3.90 + 4.2Frames and animations drawn by both versions. |
| PixiJS 8 | spritesheet JSON · animations · anchor · meta.scale | Verified PixiJS 8.21Rotated and multi-page atlases included. |
| Aseprite JSON | hash / array · frameTags · slices | Verified Phaser load.aseprite · PixiJS 8.21Tags keep their direction and repeat count. |
| .aseprite | layers · tags · durations · slices | Verified Aseprite 1.3.18Opened and rendered by the Aseprite command line. |
| Spine / libGDX | .atlas | Verified spine-canvas 4.2Every region drawn by the Spine runtime, rotated and trimmed; libGDX itself was not run. |
| Starling / Sparrow XML | XML per page | Verified Phaser 4.2Phaser 3.90 draws trimmed XML frames wrongly (its own bug); the "Sparrow XML (Phaser 3)" preset turns trim off and passes in 3.90 and 4.2. |
| LÖVE | Lua quads · nerulio_atlas.lua · main.lua | Verified LÖVE 11.5Every frame drawn and every animation stepped through the shipped helper. |
| Defold | .atlas · .tilesource | Built Defold bob.jar 1.13.1Built by Defold's command-line builder; the built texture's UVs were read back. |
| GameMaker | spr_<name>_stripN.png · gamemaker.json | UNVERIFIEDNot loaded in GameMaker (no headless GameMaker). The strips are cut the way its strip importer cuts them. |
| CSS sprites | .css · preview .html | Verified ChromiumEvery class drawn from the shipped stylesheet. |
| GIF / APNG | one file per animation | Decoded PillowEvery frame and delay decoded again after export; APNG is exact. |
Evidence
GIF decoder: 408 of 408 frames identical to Pillow on 29 real GIFs; APNG 132 of 132 on 16 files. .aseprite: 231 corpus files imported, re-written and reopened in Aseprite 1.3.18 with the same tags, durations and pixels (231/231). Exports: 49 runs in the real engines on real CC0 assets, 47 pass — the 2 failures are Phaser 3.90's trimmed-XML bug, which the Phaser 3 preset avoids.
Limits
- A grid or island guess is a preview with a confidence; nothing is cut until you press Apply, and every choice has one-click alternatives.
- .aseprite files whose layers do not compose exactly (e.g. group opacity) are imported flattened, and the Import panel says why.
- Rotated frames in an imported atlas stay rotated; their export is UNVERIFIED.
- Images up to 32,768 px per side (268 million pixels), subject to your browser's memory.
Questions
My frames drift further off with every column. What is wrong?
The sheet has spacing between frames and the engine was told 0, or it got a frame width that includes the gap. Give the measured gap to Phaser as spacing or to Unity as Padding, and the measured cell size as the frame size.
Godot's hframes and vframes cut my sheet wrong.
hframes and vframes split the whole texture into equal parts, with no margin and no spacing, so they fit only a sheet that is exactly columns × frame width wide. For any other sheet, export a SpriteFrames resource from Pack & Export: its AtlasTexture regions carry each frame's exact pixel rectangle.
The margin is different on the left and on the top.
The Studio measures X and Y separately. Unity's Offset takes both. Phaser's load.spritesheet has a single margin and a single spacing value for both axes, so for such a sheet use the Phaser atlas export instead.
Can the measured size be wrong?
Yes, which is why it comes with a confidence and alternatives rather than a silent cut. On 16 real assets imported through the UI, the default choices gave the right frames 16 times out of 16.
Is it free, and do I need an account?
Everything on these pages is free and works without an account. There is no watermark and no export that is held back.
Are my sprites uploaded?
No. The Studio decodes, packs and exports in this browser tab. Projects are autosaved in the browser (IndexedDB) and can be saved as a .nerulio file.
Does it need Aseprite or an engine plugin installed?
No. .aseprite files are read and written in the browser, and each engine bundle carries what that engine needs (for Godot, the import settings and scene; for Unity and the Godot TileSet, a small editor script).