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Paste a public asset URL to test whether this browser can fetch it with CORS, then review what that result does—and does not—mean for an HTML email.
Use free tool Free email tool
Estimate the carbon cost of your email before you send it.
Paste your email HTML and add the audience size to estimate transferred code weight and campaign emissions, then see how much trimming the HTML could save.
- No signup
- Free to use
- HTML size, estimated CO2, and optimization context
Free browser tool
Email carbon calculator
Your HTML is measured locally and is not uploaded.
How it works
From input to useful result in three steps.
- 1
Enter the number of subscribers who will receive the campaign.
- 2
Paste the final email HTML, including inline CSS.
- 3
Review the estimated code weight, transfer volume, and carbon footprint.
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Design it in Figma. Export production-ready HTML with Emailify.
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Questions
Email carbon calculator FAQ
How is the email carbon estimate calculated?
The tool measures the UTF-8 byte size of the pasted HTML, multiplies it by the audience size, and applies an indicative transfer-emissions factor. It is designed for directional comparison rather than formal carbon accounting.
Does the result include images?
Only image data embedded directly in the pasted HTML is counted. Images hosted at external URLs, tracking requests, and email-provider infrastructure are not included.
How can I reduce an email's footprint?
Start by compressing images, removing unused markup and CSS, avoiding unnecessary tracking requests, and sending relevant campaigns to a well-maintained list.
Free practical guide
How to estimate and reduce the carbon footprint of an email campaign
An email carbon calculator provides a directional estimate based on the amount of data transferred and the number of recipients. It is most valuable for comparing versions of the same campaign and identifying avoidable weight, not for producing a certified lifecycle assessment.
Quick answer
Paste the final HTML and enter the subscriber count in the free calculator above. It measures the HTML bytes, estimates campaign transfer, and applies an indicative emissions factor. Compare the result before and after removing unused code, while optimizing remote images separately.
What does an email carbon estimate measure?
The calculator measures the UTF-8 byte size of the pasted HTML and multiplies that amount by the audience size. It then applies a transfer-emissions factor to produce an indicative carbon estimate. This makes the relationship between code weight, list size, and repeated data transfer visible.
The number should be read as an estimate rather than an exact environmental total. Network mix, data-center efficiency, caching, recipient devices, reading time, storage, and provider infrastructure vary. Those factors are outside a simple browser calculation.
| Included | Not included unless embedded |
|---|---|
| HTML markup | Remote images and hosted fonts. |
| Inline CSS | Tracking requests and landing pages. |
| Embedded data inside the HTML | Sending-platform and mailbox infrastructure. |
| Audience-size multiplication | Recipient-device energy and reading time. |
How can HTML email code be made lighter?
Remove unused CSS, comments, editor metadata, duplicate declarations, and unnecessary wrapper elements after the campaign is stable. Repeated inline styles can be necessary for client compatibility, so optimization should never remove code blindly. Compare the visual and client-tested output before and after minification.
Remote imagery often outweighs the HTML itself. Resize photographs to their actual display dimensions, use an appropriate format and quality, and avoid loading several decorative images that add little meaning. Image optimization usually produces a larger practical saving than shaving a few bytes from already concise markup.
- Compress and resize images before upload.
- Remove abandoned modules and hidden campaign variants.
- Keep tracking requests purposeful and documented.
- Send to a maintained, relevant audience rather than an inflated list.
What is the best way to use the estimate?
Use the same calculator and assumptions for every version. Record the baseline HTML size, make one meaningful optimization pass, and compare the revised result at the same subscriber count. A consistent method makes relative improvement more useful than debating a single absolute number.
You can also compare template families or recurring campaign types. If one newsletter repeatedly produces much heavier code than another, inspect the module system and export process instead of optimizing each send manually.
When do you need a more detailed assessment?
A simple free calculator is appropriate for editorial decisions and production comparisons. Formal sustainability reporting requires a documented methodology that covers infrastructure, energy sources, devices, storage, organizational boundaries, and uncertainty.
Do not present this browser estimate as audited carbon accounting. Use it to make the campaign lighter, explain the direction of change, and identify where a deeper measurement exercise would need additional data.
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