About
We price the parts of cloud and AI infrastructure that nobody budgets for — and show the arithmetic.
jslet.com was registered in 2009 and previously hosted Jslet, an open-source enterprise JavaScript framework whose last public release was in 2017. The current calculator site launched in 2026. The name comes from JS + let — JavaScript-powered applets that solve real problems.
🎯 Mission
jslet builds client-side models for what cloud and AI infrastructure actually costs — the transfer fees, GPU hours, log volume, and reservation commitments that decide whether an architecture is affordable. The general developer tools on the site exist because we reach for them ourselves; the cost models exist because almost nobody publishes the arithmetic.
Every tool runs entirely in your browser. No data collection. No tracking. No sign-up walls. No vendor sponsors, no affiliate links, no AI training on your inputs. Practical utilities that work, fast — and that you can check line by line against the vendor's own pricing page.
🔧 What We Build
🔵 Cloud & AI Infrastructure Cost Models (60 calculators):
Cloud Economics — NAT gateway cost, Lambda pricing, RI vs. Spot breakeven analysis.
SRE / Availability — SLA calculators, latency budget planners, observability cost estimators.
LLM Infrastructure — GPU training cost, VRAM estimators, API pricing and self-host breakeven.
Storage & Network — RAID config analyzer, CDN cache hit ratio, IOPS→throughput, VPN overhead.
Security & DevOps — Password entropy estimators, cron frequency calculators, K8s resource planners.
Most of them answer one kind of question: why is this line item bigger than the thing it measures? The answer is rarely the price. It's the unit, the rounding, or the dimension nobody reads the docs for. That thread runs through the site as our hidden-cost series — The NAT Gateway Trap, The Observability Tax, The CI/CD Tax, The Reservation Trap, The S3 Lifecycle Trap, and about twenty more, each with the calculator that produced the numbers.
🟢 General Developer Tools (54 of the 114): JSON / CSV converters, regex visualizers, Base64 encoders, timestamp tools, CSS gradient editors, and other daily-driver utilities for frontend and full-stack developers. We keep them because we use them — not because they define the site.
Tech-Intel Briefings (40 reports): In-depth analytical reports on infrastructure-scale phenomena — AI traffic inversion, CDN economics, DNS propagation dynamics, and other under-discussed forces reshaping the operational surface of the internet.
👤 Team
jslet is built and maintained by a small crew of engineers who've put in years across cloud architecture, SRE, and software development. We build these tools because we reach for them ourselves.
No founder worship. No venture-backed growth deck. The work speaks. If a tool saves you an outage or a briefing spots a pattern six months before the herd, that's the metric.
📬 Contact
We welcome substantive technical correspondence. Bug reports with repro steps. Suggestions for new tools. Topic proposals for future briefings. Corrections when an analysis missed a beat.