How much RAM does Prometheus need? We measured: 70 MB idle
Prometheus (metrics database / monitoring) used 70 MB of RAM across 1 process sitting idle with default configuration — measured by us, on real hardware, not copied from another blog. Runtime: Single Go binary (local TSDB)
70 MB empty, but treat Prometheus as the app that grows. Give it room if you are scraping more than a handful of exporters.
What the vendors say
Prometheus documentation talks in terms of GB, and monitoring vendors recommend 4 GB upward. That advice is written for large scrape targets, not a homelab.
What changes under load
This is the app on our list where sizing genuinely matters. Memory scales with active series: an empty instance is 70 MB, but a few hundred thousand series will consume gigabytes. Budget by series count, not by our idle figure.
Methodology
Each app was started with its default configuration and an empty data directory, left to settle for 25–30 seconds, and confirmed alive with an HTTP request to its web interface. We then recorded the resident set size (RSS) of the app's entire process tree via ps. Apps were run directly on the host (no Docker), so numbers exclude container overhead (~10–30 MB with Docker).
A fresh minimal Ubuntu 24.04 VPS typically idles at roughly 200–300 MB RSS (kernel, systemd, sshd, journald). All 'fits on' verdicts below assume ~300 MB reserved for the OS.
Where to run it
A 1 GB instance from Hetzner, Vultr or DigitalOcean covers this app with the OS overhead included. Don't pay for RAM the measurements say you won't use.
Other apps we measured
File Browser (16 MB), Gotify (20 MB), ntfy (27 MB), PocketBase (31 MB), Caddy (40 MB), Navidrome (47 MB), Syncthing (57 MB), MinIO (132 MB), Uptime Kuma (136 MB), Gitea (158 MB), Forgejo (173 MB), code-server (VS Code in the browser) (191 MB)