PPTX to BMP Converter

PPTX to BMP Converter

BMP is a Windows device-independent bitmap: a header, an optional colour table, and pixel rows written more or less straight to disk. It exists on this site for the narrow but real cases where something demands a .bmp and will not take anything else — an industrial HMI panel, a laser engraver, a digital-signage controller, an installer's splash-screen slot, or a piece of in-house Windows software written against the GDI bitmap APIs. This page renders each slide of a PowerPoint deck into its own bitmap. If nothing is forcing your hand, PPTX to PNG at its Highest preset gives a true-colour result in a fraction of the space.

BMP Format at a Glance

MDN's own guidance is blunt about the web case: it warns you should typically avoid BMP for website content, because the common form is an uncompressed raster and the file sizes dwarf PNG or JPEG. That advice is worth taking literally — the numbers below show why.

What Each Quality Preset Actually Writes

BMP is the odd one out in the Quality Preset dropdown. Where other image targets expose seven rungs from Lowest to Highest, BMP offers exactly three, because the other four have no meaningful bitmap encoding behind them. The three are not a simple quality ladder either — each one produces a structurally different file.

Two things surprise people here. First, "High" is not 24-bit truecolour — a 16-bit BI_RGB bitmap is always RGB 5-5-5 in Microsoft's specification, so each channel gets 32 levels rather than 256. It is uncompressed and completely faithful to those 32,768 colours, but it is not a 24-bit master.

Second, "Low" is not reliably smaller than "Medium". Both use RLE8, which compresses horizontal runs of identical palette indices, and dithering is what destroys those runs. On a plain text slide the ranking behaves: we measured 178 KB for Medium and 167 KB for Low. On a slide with a soft gradient background — the default look of most corporate templates — it inverts, because Medium smooths the gradient slightly before quantizing while Low dithers an 86-colour palette across it: 3.7 MB for Medium against 4.4 MB for Low, an 18% penalty for choosing the "smaller" preset. On a full-bleed photographic slide, RLE8 gives up almost entirely and both land near 13 MB.

How to Convert PPTX to BMP

1. Upload Your PPTX File: Drag the .pptx onto the page or click "+ Add Files". Every slide is rendered separately, so a 10-slide deck returns 10 bitmaps plus a "Download All (Zip)" button.
2. Choose a Quality Preset: Open Advanced Options and pick High, Medium or Low. High is the uncompressed 16-bit bitmap that every decoder handles; Medium and Low write RLE8-compressed palette bitmaps that are far smaller but rely on run-length support in whatever reads them.
3. Set Image Resolution (Optional): Image resolution starts on "Keep original" and gives you the full 300 DPI render. Preset Resolutions, Resolution Percentage, or an exact Width × Height all cut the pixel count — the fastest way to make a bitmap smaller.
4. Convert and Download: Click Convert and save the bitmaps individually or as a zip. No sign-up, no watermark.

Why the Files Are So Large

Slides render at a fixed 300 DPI. There is no DPI control on this page, so the pixel dimensions follow directly from the slide size you chose in PowerPoint, and an uncompressed bitmap's size follows directly from that.

Microsoft's own formula for an uncompressed DIB is stride = ((width × bits-per-pixel + 31) & ~31) ÷ 8, with the pixel array occupying height × stride bytes on top of the 54-byte header. Run it for a default Widescreen slide at the High preset and the answer is exact:

We converted a three-slide Widescreen deck through this route and each bitmap came back at exactly 18,000,054 bytes — the formula and the output agree to the byte, because there is nothing adaptive about an uncompressed bitmap. Halving the resolution quarters the file; nothing else moves the number.

Frequently Asked Questions

Why does BMP only offer three quality presets when other formats offer seven?

Because a bitmap has almost no quality dial to turn. The three presets map to three genuinely different encodings — 16-bit uncompressed, 256-colour RLE8, and 86-colour RLE8 — and the remaining rungs have no bitmap equivalent, so they are not shown. There is also no "Specific file size" mode on this page for the same reason: with a fixed bit depth and no lossy encoder, the only lever on size is the pixel count.

Is the BMP output really uncompressed?

Only at the High preset, which writes BI_RGB — Microsoft's value for "uncompressed RGB". Medium and Low both write BI_RLE8, a run-length scheme that packs repeated palette indices into two-byte pairs. On flat, poster-style slides that is a huge win; on photographic content the runs are too short to help, and the encoded data can end up larger than the raw palette indices would have been.

Which preset should I pick if the bitmap has to open in something old?

High. A 16-bit uncompressed BI_RGB bitmap with a plain 40-byte header is the most conservative thing this converter can write, and it is what a minimal GDI-era or embedded decoder is most likely to accept. MDN notes that the more efficient BMP variants are rarely supported in browsers, and the same caution applies to simple firmware decoders — if the target chokes on Medium or Low, RLE support is the usual reason.

Do I get one bitmap per slide or one file for the deck?

One per slide, numbered in slide order. BMP has no multi-page concept at all, so a 24-slide deck is 24 files; use the "Download All (Zip)" button to take them in one go. For a single file holding every slide, PPTX to PDF is the right target.

Can a BMP keep a transparent slide background?

Not from this converter. Alpha in BMP only exists in the 32-bit variant, and none of the three presets writes one — transparent regions are resolved during rendering. If you need genuine transparency for compositing, PPTX to PNG carries a full alpha channel and is smaller besides.

How do I get a smaller BMP without changing the preset?

Reduce the pixel count. Because file size is a direct product of width, height and bit depth, dropping Image resolution to a 1080p preset takes a 4000 × 2250 High-preset bitmap from about 17 MiB to roughly 4 MiB, with no encoding trade-off at all. That is a far bigger lever than any preset change, and it is the one to reach for first.

Why is the "Low" preset sometimes bigger than "Medium"?

Because both compress with RLE8 and Low dithers harder. Run-length encoding only pays when neighbouring pixels share a palette index, and Floyd–Steinberg dithering deliberately scatters indices to fake missing colours. Squeezing a gradient into 86 colours produces far more dither noise than squeezing it into 256, so the runs break up and the file grows. Medium also smooths the image slightly before quantizing, which lengthens runs further.

Can I convert the bitmaps back into something smaller afterwards?

Yes, and it is often the right move: render at High so nothing is quantized, then run the results through BMP to PNG — its Highest preset writes a true-colour PNG a fraction of the size — or compress BMP if the .bmp extension itself has to stay. Going the other way — starting from Low and hoping to recover detail — cannot work, since the 86-colour quantization is permanent.

How large a deck can I upload, and what happens to it afterwards?

There is no slide-count limit; upload size and connection speed are the practical constraints, since rendering happens on our side. Files are uploaded over an encrypted connection, processed on our servers, and deleted automatically after a few hours — no sign-up, no watermark, never shared or made public.