No — DPI does not directly affect file size. DPI (dots per inch) is metadata that tells printers how large to render the image. A 1920×1080 image at 72 DPI and the same image at 300 DPI have identical pixel data and file size (barring a few bytes of metadata difference). Only pixel dimensions (width × height) determine the actual image data size. DPI only matters for print output dimensions.

Use JPEG for photographs and natural images — it achieves excellent compression with minimal visible quality loss. Use PNG for graphics, logos, screenshots, and images requiring transparency — it preserves sharp edges and text perfectly. PNG is lossless, so it's also preferred when you need to preserve exact pixel data. For the web, consider WebP as a modern alternative that handles both use cases well.

Megapixels (MP) = (width × height) ÷ 1,000,000. For example, 1920×1080 = 2.07 MP, 3840×2160 = 8.29 MP, and a 12MP smartphone photo is typically around 4000×3000 pixels. Our tool displays the MP value automatically as you enter dimensions. Most modern smartphone cameras produce 12-48 MP images, while professional DSLRs can reach 50+ MP.

WebP is a modern image format by Google that supports both lossy and lossless compression. It's now supported by 97%+ of browsers (Chrome, Firefox, Edge, Safari 14+). WebP lossy images are 25-35% smaller than JPEG at the same quality, and WebP lossless images are ~26% smaller than PNG. It also supports transparency and animation. For most websites today, serving WebP with JPEG/PNG fallbacks is the recommended best practice.