Runtime

Fly Machines vs Runloop: pricing, devboxes and limits

A 2 CPU, 4 GB Runloop devbox costs $0.3195 an hour; a Fly Machine of that size costs $0.0861. Runloop adds agent benchmarks.

Runtime runs the same job for 55% less than a Fly Machine and 88% less than Runloop. 1,000 one-minute runs of a 2 vCPU, 4 GiB sandbox cost $1.44 on Fly Machines, $5.33 on Runloop and $0.64 on Runtime, because Runtime bills the CPU your code uses rather than the CPUs it holds. A paused Runtime sandbox keeps its memory and running processes, which neither rival's suspend does at this size. Rates checked 23 September 2026.

Estimated compute cost

55% less than Fly Machines88% less than Runloop

2 vCPUs · 4 GiB · 60 s a run · 20 CPU-seconds busy

1,000

Compute only, at list rates checked 23 September 2026 (Fly.io pricing, Runloop pricing). Plan fees, network, taxes and free credits are left out. The worked example below shows the arithmetic.

At a glance

Fly Machines Runloop Runtime
Isolation Firecracker microVM microVM, with a container inside Firecracker microVM, own kernel
CPU Inside a fixed size, billed while started $0.108 per CPU-hour while the devbox runs $0.025 per vCPU-hour of measured CPU, with a small floor
Memory Inside the size; more at $5 per GB a month $0.0252 per GB-hour $0.0075 per reserved GiB-hour
Disk Root disk temporary; Fly Volumes for files that last $0.00034236 per GB-hour; MEDIUM comes with 8 GB Included while running
2 vCPU, 4 GB performance-2x, $0.0861 an hour (iad) MEDIUM, $0.3195 an hour $0.08 an hour fully busy, $0.03125 waiting
Sizes Fixed sizes up to 16 performance vCPUs and 128 GB X_SMALL to XX_LARGE, or custom up to 16 CPUs, 64 GiB vCPUs and memory chosen per sandbox
Plan fee None; pay as you go Basic free; Pro $250 a month plus usage None; prepaid credit from $10
Free start Not stated on the pricing page $50 of credit, no card 50 sandbox hours, no card
Suspend, resume Keeps memory only for Machines with 2 GB or less Keeps the disk; processes restart Pause keeps files, memory and processes, 1 to 365 days

Why does a Runloop devbox cost almost four times a Machine?

The rates. Runloop bills $0.108 per CPU-hour, $0.0252 per GB-hour of memory and its disk by the GB-hour, so its MEDIUM devbox, 2 CPUs, 4 GB and 8 GB of disk, comes to $0.3195 an hour. A Fly performance-2x with 4 GB is $0.0861, about 27% of that. Both bill the whole size for as long as it runs, busy or waiting.

What the premium buys is around the VM rather than in it: Runloop runs SWE-Bench and other public benchmarks, builds custom ones from your data, deploys into your own cloud account and states SOC 2, HIPAA and GDPR readiness. A Fly Machine is a general-purpose VM in 18 regions, with volumes and Managed Postgres in the same account.

Runtime is priced below both for agent work, since it bills measured CPU at $0.025 a vCPU-hour; agent evals and SWE-bench shows how to run a benchmark harness on it.

Cost for the same job

1,000 runs of a 2 vCPU, 4 GiB sandbox. Each run lasts 60 seconds and keeps the CPU busy for 20 CPU-seconds: an agent that mostly waits for a model. The Fly Machine is a performance-2x with 4 GB; the Runloop devbox is a MEDIUM.

TextMachines  Size   1,000 × 60 s / 3,600 × $0.0861           = $1.44Runloop   CPU    1,000 × 60 s / 3,600 × 2 × $0.108        = $3.60          Memory 1,000 × 60 s / 3,600 × 4 × $0.0252       = $1.68          Disk   1,000 × 60 s / 3,600 × 8 × $0.00034236   = $0.05          Total                                              $5.33Runtime   CPU    1,000 × 20 s / 3,600 × $0.025            = $0.14          Memory 1,000 × 60 s / 3,600 × 4 × $0.0075       = $0.50          Total                                              $0.64

At 100,000 runs a month that is $143.50 on Fly Machines, $532.56 on Runloop and $63.89 on Runtime. With both CPUs busy for the whole minute, it is $1.33 on Runtime against $1.44 on Machines and $5.33 on Runloop, so Runtime is cheaper however busy the sandbox is. Plan fees, storage while suspended, network and free credits are left out.

What survives a suspend?

On Runloop, only the disk. Its lifecycle docs say in-memory state is not kept across suspend and resume, though the devbox keeps its ID and SSH keys, and a suspended devbox is charged for storage until it is shut down. Compute stops while it is suspended.

A Fly Machine's suspend keeps the whole VM, memory and open files included, and resumes in a few hundred milliseconds, but it needs 2 GB of memory or less, so the 4 GB size here only stops. Fly also says a deploy, a host migration or maintenance discards a suspended snapshot.

A paused Runtime sandbox keeps its files, memory and running processes at any size, for 1 to 365 days, at $0.08 per GB a month, and a request to it wakes it by itself.

Which one to pick

  • Pick Fly Machines for a service that stays up near its users, at a low hourly price, in any of 18 regions.
  • Pick Runloop if you want benchmarks run for you, a deployment in your own cloud, or a stated compliance posture.
  • Pick Runtime for agent sandboxes that pause and resume with their processes still running, measured CPU, and no plan fee.

Switch from either one

A suspended devbox that must restart its processes becomes a paused sandbox that carries on where it stopped:

TypeScriptimport { Sandbox } from "withruntime";const sbx = await Sandbox.create({ funding: "trial", timeoutSeconds: 600 });await sbx.exec("echo state > /workspace/state.txt");await sbx.pause(); // memory, files and processes kept; compute billing stopsconst again = await Sandbox.connect(sbx.id);await again.wake({ timeoutSeconds: 1200 });console.log((await again.exec("cat /workspace/state.txt")).stdout);await again.stop();

Or give your coding agent the one instruction in migration: it switches the project on a branch, tests it on the free trial and reports the monthly saving. npx withruntime compare --from fly-machines (or --from runloop) prices what you ran at the old provider's rates, and npx withruntime switch --from fly before your first top-up matches that top-up with credit, up to $100. The full side-by-sides are Runtime vs Fly.io and Runtime vs Runloop.

Sources

Rates checked 23 September 2026; the Fly suspend page and Runloop's sizes and lifecycle pages read 25 September 2026.

Facts on this page were checked on 25 September 2026.

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