PNG to JPG Converter: Convert PNG Images to JPEG Online

Convert PNG to JPG

PNG files are lossless, which is exactly what you want for screenshots, diagrams, and anything with text. But for photographs and complex images, PNG’s lossless compression produces files far larger than necessary. A 5 MB PNG photograph compresses to 300-500 KB as a JPEG at quality 85, with no visible difference at normal viewing sizes.

This tool converts PNG to JPG entirely in your browser. Drop a file, adjust the quality slider, and download the result. Nothing is uploaded to a server.

How JPEG Compression Works

JPEG compression operates in several stages that exploit how human vision processes images.

First, the image is converted from RGB to YCbCr color space, separating brightness (luminance) from color (chrominance). Human eyes are far more sensitive to brightness changes than color changes, so the chrominance channels are downsampled to half resolution with little perceptible impact.

Next, the image is divided into 8x8 pixel blocks. Each block is transformed using a Discrete Cosine Transform (DCT), which converts spatial pixel data into frequency components. High-frequency components represent fine detail and sharp transitions.

The quality slider controls a quantization step that divides these frequency components by a scaling factor, rounding to integers. Higher quality means smaller divisors, preserving more frequency data. Lower quality means larger divisors, which zeros out high-frequency components and produces smaller files at the cost of fine detail.

This is why JPEG artifacts appear as blocky smearing around sharp edges: the 8x8 block boundaries become visible when too much high-frequency data is discarded.

The Transparency Problem

PNG supports a full alpha channel where each pixel can be fully transparent, fully opaque, or anywhere in between. JPEG has no concept of transparency.

When this tool converts your PNG to JPG, transparent pixels are composited against a white background. If your PNG has a colored subject on a transparent background, the result will have that subject on a white background.

This matters for logos, icons, and product images designed to float over any background color. If you need lossy compression with transparency, convert to WebP instead. WebP supports both lossy compression and alpha channels.

Quality Settings Guide

The quality slider maps directly to JPEG’s quantization tables. Here is what different ranges produce in practice:

95 to 100

Near-lossless. File sizes are 2-3x smaller than PNG for photos but still large. Use this for archival or print preparation where you need JPEG format but maximum fidelity.

80 to 90

The sweet spot for web images. Files are typically 10-20x smaller than the PNG source. Compression artifacts are invisible at normal viewing distances. This is what most image optimization pipelines target.

60 to 79

Visible compression on close inspection, but acceptable for thumbnails, social media previews, and situations where bandwidth matters more than pixel-level quality.

Below 60

Heavy artifacts. Useful for placeholder images, extreme bandwidth constraints, or intentional aesthetic effects.

PNG vs JPG: When to Use Each

The decision is straightforward once you understand what each format optimizes for.

Keep as PNG

When the image contains text, line art, screenshots of UIs, diagrams, or anything with sharp edges between flat color regions. PNG’s lossless compression preserves these features perfectly, and JPEG’s block-based compression visibly degrades them.

Convert to JPG

When the image is a photograph, gradient-heavy artwork, or any image where slight detail loss is acceptable. The file size reduction is dramatic: a typical photograph compresses from 2-5 MB as PNG to 100-400 KB as JPEG.

Consider WebP

When you want the best of both. WebP’s lossy mode produces files 25-35% smaller than JPEG at equivalent visual quality, and it supports transparency. See the PNG to WebP converter for that workflow.

File Size Expectations

These numbers assume photographic content. PNGs with large flat color areas (like screenshots) compress to even smaller JPEGs because the DCT efficiently encodes uniform regions.

For more format options, see the full Image Converter. To encode images as Base64 strings for embedding in HTML or CSS, use the Base64 Encoder.