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Probably the best Lightsail money-saver: turn $92/TB overage into $2.50/TB (free & open source)
Last year I was running a small file-distribution service on Lightsail in us-east-1. One month downloads spiked, and the bill came with $500 in data transfer overage.
The painful part: that was about 5.4 TB over the allowance, and three extra $5 IPv6-only instances (2 TB each, $15/month total) would have covered all of it.
Quick recap of how Lightsail transfer works (AWS docs + AWS Support answers on re:Post):
- Inbound and outbound both count toward the allowance, but only outbound overage is billed: $0.09/GB in US/EU regions, up to $0.17/GB in Sydney. That's ~$92/TB.
- Same region + same bundle size = one shared pool. Dual-stack and IPv6-only instances of the same size pool together.
- A $5 IPv6-only instance comes with 2 TB, so extra allowance costs ~$2.50/TB.
- Billing is hourly; an instance added mid-month gets a prorated allowance.
- Overage already incurred can't be offset later, so you need to add capacity before you run out.
- Deleting and recreating an instance does not reset this month's usage.
The trick is simple; doing the math every month isn't. So I built a calculator:
Enter the data used so far this month (or just an expected monthly total) and it tells you:
- whether you're safe, heading for overage, or already over, and how much it'll cost
- when the allowance runs out
- how many same-size traffic instances to add for the lowest total cost (compares adding 0/1/2/3, one click to apply)
- what to run next month at the current pace
Example: at the current pace this month goes 440 GB over, costing $39.58. Adding 2 traffic instances today costs $1.79, saving $37.79.
Works with AI agents. The "Use with AI" button gives you a prompt to paste into ChatGPT / Claude / Gemini / Cursor. The agent reads the site's llms.txt, runs the same rules and hands back a pre-filled link you can check. If you'd rather script it, the calculation module (calc.js) and prices (prices.json) are static files you can import cross-origin. No API key.
Free, open source, self-hostable. It's a static single page; your data stays in your browser. Host your own copy on Cloudflare Workers or Vercel (free tiers are plenty), or with Docker (amd64 + arm64):
docker run -d -p 8080:80 imxjp/lightsail-cost-saver
Source: https://github.com/yt1988/lightsail-cost-saver
Covers all 19 Lightsail regions (half-allowance regions included), 10 languages, light/dark mode, works on mobile. Estimates only; your AWS bill is final. Feedback, corrections and feature requests very welcome.
Comments
smart.
Now this is a good vibe coded project
Does it have to be the same bundle size? Iirc just being in the same region was enough
Unfortunately, according to AWS’s official documentation, only instances in the same region and of the same size can share a data transfer pool.
In fact, the tool’s page also provides plenty of links to official information. It’s also an excellent piece of middleware: beyond direct queries, it works well with AI agents for tasks such as automated alerts and scaling.
Because this is so complicated and could lead to a very costly bill, I spent time building this calculator in the hope that it can help others who’ve had similar frustrating experiences.
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https://docs.aws.amazon.com/lightsail/latest/userguide/amazon-lightsail-faq-data-transfer-allowance.html#data-transfer-allowance-how-does-my-data-transfer-allowance-work-for-instances
Example 3 – You create two sets of instance bundles: set A with two $5 USD per month instance bundles (bundleId nano_3_0) and set B with three $7 USD per month instance bundles (bundleId micro_3_0), both in the US West (Oregon) Region. In aggregate, this gives you 2 TB of data transfer allowance for set A, and 6 TB of data transfer allowance for set B. If you transfer 3 TB of data to the Internet through set A instances and 4 TB of data to the Internet through Set B instances, you will exceed your data transfer allowance for Set A instances and will be charged a data transfer OUT overage fee for 1 TB. You will still be within your allowance for Set B instances by 2 TB.
Hmmm I'm pretty sure this wasn't the case when Lightsail was first introduced (I'd just add additional $5 VMs just to add additional bandwidth). They must have added to discourage people like me lol
thank you for the update!
Thank you for the kind words. I’m happy to help anyone who needs it.
Can this be summarized in 3 sentences? What is this?
aws costs calculator
don't use aws, use LET providers
Just a simple calculator?
sophisticated calculator.
is a free, open-source web calculator that helps AWS Lightsail users reduce bandwidth costs by optimizing their shared data transfer allowances.
It forecasts monthly traffic usage, estimates overage charges, and recommends the cheapest number of additional instances to avoid expensive bandwidth fees.
The tool supports 10 languages, requires no registration, runs entirely in your browser, and can be self-hosted using Docker or Cloudflare.
I completely agree. This is just a tool for the few people who need it.
Big tec don't care about 7 dollar per year customers. They rather loose them.
Using a VPS with 2-10TB would allready match the situation. With a script you could bind every vps in to that pool if needed.