Responsive Image srcset & sizes Attribute Calculator
Calculate responsive pixel widths, target device pixel ratios (1x, 2x, 3x), media query breakpoints, and copyable HTML5 markup with bandwidth savings analysis.
Image Dimensions & Container Layout
px
Mobile Payload Data Reduction
90% DATA SAVED
~90% Data Saved
Mobile 390px 2x screen loads ~56 KB candidate instead of 576 KB master
Generated HTML5 Markup
<!-- Loading... -->
Candidate Files & Density Mapping
Generated Sizes Attribute:
100vw
Export Widths (w-descriptors):
320w, 640w, 960w, 1280w, 1920w, 2560w
Default Fallback Dimensions:
width="1280" height="720"
Core Web Vitals LCP Note:
Above the fold: use fetchpriority="high"