BMP to PNG

Convert supported BMP to PNG locally with explicit alpha handling, resize controls and batch downloads.

Choose up to 20 BMP images or drop them here

10 MiB per file · 50 MiB per batch · 12 million pixels and 8,192px per side. Conversion stays in this browser.

Maximum edge

PNG preserves decoded pixels and supported transparency; resizing changes pixels, and PNG may be larger. Images are never enlarged; original metadata is not copied.

Uncompressed 1/4/8/16/24/32-bit BMP and 16/32-bit bitfields are supported. Explicit alpha masks are preserved; ordinary 32-bit BMP without an alpha mask is opaque. RLE and color-profile BMP require re-export.

This tool runs entirely in your browser. Your data is never uploaded, never stored, and never leaves your device.

BMP to PNG reads supported bitmap rows, palettes and explicit alpha correctly and creates a losslessly encoded PNG, with optional downscaling and batch downloads.

How to use it

1Select supported BMP screenshots, diagrams or application exports.
2Choose Original dimensions to retain the decoded pixel size, or reduce the maximum edge.
3Convert, inspect the preview, and download PNG results or one ZIP of successful files.

Example

Input: 3 × 2 padded-row 24-bit BMP
Output: 3 × 2 PNG with matching decoded RGB pixels

Original dimensions preserves the decoded raster; metadata is not copied.

What happens to your data

Bitmap headers and pixels are decoded on your device. PNG results and ZIP archives remain temporary in the browser until you download them.

Last updated October 2026

Convert a Windows bitmap into PNG for a screenshot, diagram, legacy application image or compatible upload. Original dimensions keeps the bitmap's decoded size; optional maximum-edge resizing makes a smaller copy without cropping. Review each result and download it directly, or create a ZIP for a small batch.

PNG is a practical output for bitmap text and line art because its encoding does not add JPEG-style artifacts. Explicit, supported BMP alpha is retained. Ordinary bitmap padding and unused fourth bytes do not become a transparent background, and an opaque source stays opaque.

How it works

The local BMP decoder handles padded rows and bottom-up or top-down storage directly. Supported sources include uncompressed 1/4/8-bit palettes, 16/24/32-bit color and 16/32-bit bitfields with valid channel masks. The decoder checks dimensions, planes, palette length, color-mask overlap and every pixel row before generating a PNG. A palette pixel referring to a missing color is an error, not a black replacement.

Sources are capped at 10 MiB each, 20 files and 50 MiB per batch, with raster limits of 12 million pixels and 8,192 pixels per side. Unsupported RLE or embedded JPEG/PNG compression, and BMP files declaring calibrated or embedded color profiles, need an sRGB uncompressed re-export. These restrictions are explicit because silently treating unusual data as ordinary pixels can change the image.

With Original dimensions, the PNG stores the supported decoded pixels without another lossy encoding step. Reducing the maximum edge resamples those pixels first. A 3 × 2 bitmap retains 3 × 2 dimensions when a 640-pixel maximum is selected; smaller inputs are never enlarged. When a valid alpha mask exists in a supported bitfields bitmap, the PNG preserves its alpha. The checkerboard is only a preview background.

The output does not copy the original BMP metadata or profile. Actual byte counts show whether PNG reduced size; no reduction is guaranteed. Successful files remain available if another input fails. A 60 MiB combined output guard bounds the batch, safe flat names prevent archive path entries, and numbered duplicates avoid overwriting. Replacing input, adjusting settings or cancelling removes stale results.

Worked example: Preserve a small padded-row bitmap

Input: 3 × 2 uncompressed 24-bit BMP; maximum edge 640
Result: 3 × 2 PNG with the same decoded RGB pixels

Row padding and bottom-up storage are checked against the downloaded PNG.

Common use cases

Keeping sharp text and line art from a BMP screenshot
Making old bitmap exports usable in a PNG-only workflow
Preserving explicit BMP alpha in a compatible format
Packaging a small set of bitmap diagrams as named PNG files

Frequently asked questions

Is BMP to PNG lossless?＋

PNG encoding is lossless for the supported decoded pixel values. Select Original dimensions to avoid a resize. The converter does not preserve original metadata, color-profile information or unsupported BMP variants.

Will the PNG have a transparent background?＋

Only if the supported BMP has an explicit valid alpha mask. Standard 24-bit BMP and ordinary 32-bit BMP without an alpha mask remain opaque. Converting formats does not remove an image background.

Why does my BMP look upside down in some converters?＋

Most BMP pixel rows are stored bottom-up; a negative height indicates top-down storage. This decoder reads the declared direction and row padding explicitly, then writes the PNG in normal display order.

Can I convert an RLE-compressed BMP?＋

Not in this workflow. Export it as an uncompressed sRGB BMP from an image application first, then convert that file. The page also rejects embedded JPEG/PNG compression and unsupported profile variants.

Is PNG always smaller than BMP?＋

No. PNG often compresses flat colors and diagrams well, but the outcome depends on the source. The actual before/after byte counts show the result for your file.

Can I convert several BMP files locally?＋

Yes. Select up to 20 files within the individual and combined limits, convert, then review and Prepare ZIP. Failed inputs are listed separately and do not enter the archive.