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Image Optimization Calculator

Compare image format savings and their effect on page load.

About Image Optimization Calculator

Format conversion and correct sizing multiply rather than add, so combining them typically removes two thirds of image weight. Because images are usually the largest contentful element, the saving translates almost directly into LCP. Correct sizing usually saves more than format conversion, and it is often overlooked because the oversized image still looks correct on screen.

Formula

Image Optimization

Optimised weight = original × (1 − format saving) × (1 − sizing saving)

AVIF
Around 50 per cent smaller than JPEG at equivalent quality
responsive sizing
Serving images at display size rather than full resolution

Worked example

With the default values below, Image Optimization Calculator returns Optimised Weight of 585.00. Change any input above and every figure here is recalculated in your browser.

Inputs used

Original image weightminimum 0 KB
1,800 KB
Target formatone of WebP, AVIF, JPEG XL, Optimised JPEG
AVIF
Additional saving from correct sizingaccepts 0–90 %
35 %
Connection speedminimum 0.01 Mbps
10 Mbps
Monthly pageviewsminimum 0
200,000

Results

Optimised Weight
585.00 KB
Saving From Format Alone
50.0%
Total Weight Reduction
67.50%
Estimated LCP Improvement
972 ms
Monthly Bandwidth Saved
231.743 GB

Step by step

  1. 1Values used
  2. 2Image Optimization
  3. 3Optimised Weight= 585.00 KB
  4. 4Saving From Format Alone= 50.0
  5. 5Total Weight Reduction= 67.50
  6. 6Estimated LCP Improvement= 972 ms
  7. 7Monthly Bandwidth Saved= 231.743 GB

Assumptions and limits

  • The result is derived only from the 5 inputs listed above. Anything not among them is not part of the calculation.
  • In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
  • Figures are rounded for display to 3 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Frequently Asked Questions

How is Image Optimization calculated?

Optimised weight = original × (1 − format saving) × (1 − sizing saving) Format conversion and correct sizing multiply rather than add, so combining them typically removes two thirds of image weight. Because images are usually the largest contentful element, the saving translates almost directly into LCP.

Why does Image Optimization matter?

Correct sizing usually saves more than format conversion, and it is often overlooked because the oversized image still looks correct on screen.

What values do I need to enter?

This calculator takes 5 inputs: Original image weight, Target format, Additional saving from correct sizing, Connection speed, Monthly pageviews. The pre-filled defaults are a realistic starting point — replace them with figures from your own environment for a result you can act on.

Related Calculators

Image Optimization Calculator – Calculate Optimised Weight