The Email Cost Calculator is one engine with many landings. SES and Cloudflare pages pass a default vendor; the math does not fork.
Inputs that change the bill
Emails per month is the volume. For Amazon SES that number is recipients. For Cloudflare and ESP SKUs it is messages against an included quota.
Already on Workers Paid only affects Cloudflare. Public Email Sending requires Paid. If you already run Workers, leave it checked so the $5 floor is omitted. If Email Sending is why you would upgrade, uncheck it — fixture D is $5 + overage.
SES free allowance defaults to none. First-12-months 3,000 messages and the legacy EC2 62,000/month option exist because those are real AWS footnotes — they are not assumed.
Attachment GB is SES data at $0.12/GB in the card.
USD → INR is the rate you type. There is no live FX feed.
How a vendor row is chosen
For Resend, SendGrid, Postmark, and Mailgun the engine lists modeled SKUs, drops any that cannot send the volume (hard cap or daily cap), and keeps the lowest monthly USD. That is why Postmark at 50k is Platform ($66) in the tests, not the Pro illustration ($68.50) from the cluster notes.
Cloudflare is special-cased: 3,000 included, overage, optional Paid floor, optional verified-destination zero.
SES is special-cased: billable = volume minus optional free allowance, times the unit rate, plus attachments.
Infeasible SKUs (for example a free plan that cannot cover the month) sink to the bottom of the table.
What you should not read into the highlight
“Cheapest” means cheapest in this model at this volume on this dated card. It is not a forever ranking, not including dedicated IPs, and not your invoice. Confirm on the vendor’s pricing page — every vendor name in the table links out.
Presets: AWS SES Cost Calculator, Cloudflare Email Cost Calculator. Hub: Email Sending Cost.