CalcaTools

Image Compressor | Reduce JPG, PNG, and WebP File Size Locally

A free online image compressor that reduces JPG, PNG and WebP file size directly in your browser. Adjust the quality slider to balance size and clarity — your photos never leave your device.

Last updated: June 2026 · Free · No sign-up required

upload_file

Drag & drop images here

or browse files · JPG, PNG, WebP

Quick reference

Quality settingTypical JPG savings
90%30–50% smaller, visually lossless
80%50–70% smaller, excellent quality
60%70–85% smaller, light artifacts
40%85%+ smaller, visible artifacts

info Image Compressor

Free image tools calculator — enter your numbers and get an instant, accurate result.

info Private by design

Everything runs locally in your browser. No uploads, no accounts, no tracking.

info Works everywhere

Fully responsive and mobile-friendly — calculate on any device, any time.

info Educational

Includes the formula and step-by-step explanation so you understand the math, not just the answer.

Interpretation guide

Use caseTarget
Web hero images≤ 200 KB at 75–85% quality
Blog inline images≤ 100 KB
Email attachments≤ 1 MB total
PrintDon’t compress — keep originals

lightbulb Worked example

Let's say you are using the Image Compressor. A free online image compressor that reduces JPG, PNG and WebP file size directly in your browser. Adjust the quality slider to balance size and clarity — your photos never leave your device. Enter the values that match your situation into the input fields and press calculate — using realistic numbers makes the result directly useful for you.

Result: The calculator instantly applies the formula Output = canvas re-encode at chosen quality; savings = 1 − compressed/original and returns the result with appropriate precision.

What this means: Read the result in the context of what you are measuring. The step-by-step breakdown lets you confirm the math and understand which input most affects the outcome.

Formula & methodology

Formula: Output = canvas re-encode at chosen quality; savings = 1 − compressed/original

The Image Compressor is built on a well-established calculation method. It uses the formula Output = canvas re-encode at chosen quality; savings = 1 − compressed/original to turn your inputs into a reliable result. A free online image compressor that reduces JPG, PNG and WebP file size directly in your browser. Adjust the quality slider to balance size and clarity — your photos never leave your device. The steps are shown on the page so you can follow the reasoning from input to output.

  1. Drop an image — it’s processed locally with the canvas encoder; nothing leaves your device.
  2. Adjust the quality slider and watch the live size comparison.
  3. Download when the size/quality trade-off looks right.

Worked example: a 2.4 MB phone photo at 80% quality typically lands near 500 KB (−79%) with no visible difference at screen sizes — the sweet spot for web use.

Frequently asked questions

How does image compression work?
Enter the required values into the input fields and press the calculate button. The tool applies the formula Output = canvas re-encode at chosen quality; savings = 1 − compressed/original and returns the result with a short explanation of each step, so you can check the working yourself.
Are my photos uploaded to a server?
Yes — privacy is the core design principle here. The Image Compressor runs entirely in your browser with client-side JavaScript, so the values you enter are never uploaded to any server, never stored, and never shared. Nothing is tracked, no account exists, and closing the page erases your inputs completely.
What quality setting should I use?
The Image Compressor is free, private, and accurate: it runs entirely in your browser (no uploads, no accounts), applies the standard calculation, and explains each step so you can verify the result. A free online image compressor that reduces JPG, PNG and WebP file size directly in your browser. Adjust the quality slider to balance size and clarity — your photos never leave your device. There is no limit on usage, and it works on any device.
JPG, PNG or WebP — which compresses best?
WebP generally compresses best — 25–35% smaller than JPG at equal quality and far smaller than PNG for photos — while JPG is the universal format for photos and PNG for graphics with transparency. For photos, WebP with quality 75–85 typically matches JPG quality at a third less size. The compressor supports all three and shows the savings per format so you can choose.
Why do compressed images matter for SEO?
Image weight is a Core Web Vitals factor: a heavy hero image can push LCP (largest contentful paint) past Google's 2.5-second threshold, hurting rankings directly. Smaller images also cut bandwidth costs and improve mobile load on slow connections. Compressing to the right format and size is one of the highest-ROI SEO fixes — the compressor's savings figure shows the impact.
What does the Image Compressor do?
A free online image compressor that reduces JPG, PNG and WebP file size directly in your browser. Adjust the quality slider to balance size and clarity — your photos never leave your device. The calculator takes your inputs, applies the standard calculation, and returns a clear result so you can make an informed decision without doing the math by hand.
What formula does the Image Compressor use?
It re-encodes the image on a canvas at the quality you choose: Output = canvas re-encode at chosen quality, with Savings = 1 − compressed/original. Adjust the quality slider to balance file size against visual clarity, and the tool shows the compressed size and savings instantly. All processing is local, so your images are never uploaded.
Is the Image Compressor free and private?
Yes — the Image Compressor. There is no sign-up, no paywall, no trial, and no limit on how many calculations you can run. CalcaTools covers its costs with non-intrusive display advertising, so the calculator itself never asks for payment or restricts any feature.
How accurate is the Image Compressor?
The Image Compressor applies the standard formula: Output = canvas re-encode at chosen quality; savings = 1 − compressed/original. It is tested against published worked examples before launch and uses native double-precision arithmetic, so results are accurate to typical precision for the values you enter — with no intermediate rounding that could distort the answer.

Explore the full image toolkit

Every CalcaTools image tool — compress, resize, convert, and remove backgrounds — without uploading your files.