Runtime costs 73% less than Fly Sprites for an agent that waits on a model. 100,000 one-minute runs of a 2 vCPU, 4 GiB sandbox, each using 20 CPU-seconds, cost $63.89 a month on Runtime and $240.14 on Sprites. Both bill measured CPU, and both run Firecracker microVMs. Runtime's rates are lower on each meter. Rates checked 25 October 2026.
How Fly Sprites bill
Sprites are Fly.io's sandboxes for agents. Like Runtime, they bill CPU only while it works. Memory is billed on what the Sprite actually uses. Fly manages how much that is, so it is not a figure you set.
| Meter | Fly Sprites | Runtime |
|---|---|---|
| CPU | $0.0385 per CPU-hour, measured | $0.025 per vCPU-hour, measured, floor 0.05 of a vCPU |
| Memory | $0.021875 per GB-hour of memory in use | $0.0075 per reserved GiB-hour |
Runtime's CPU rate is 35% below Sprites' and its memory rate 66% below. The calculator assumes a Sprite uses all the memory you enter for the whole run, priced as decimal GB. A Sprite that uses less pays less for memory. At 4 GB in use, a Sprite's memory alone costs $0.087 an hour. A whole 2 vCPU, 4 GiB Runtime sandbox costs $0.03125 an hour while it waits and $0.08 with both CPUs busy.
Example workloads
A month of each, CPU and memory only, from the calculator above.
| Workload | Runtime | Fly Sprites |
|---|---|---|
| Agent runs: 2 vCPU, 4 GiB, 60 s, 20 CPU-seconds, 100,000 a month | $63.89 | $240.14 |
| Every CPU busy: 2 vCPU, 4 GiB, 60 s, 120 CPU-seconds, 100,000 | $133.33 | $347.08 |
| Tool calls: 1 vCPU, 2 GiB, 2 min, 30 CPU-seconds, 50,000 | $35.42 | $107.19 |
| Waiting agents: 2 vCPU, 4 GiB, 30 min, 180 CPU-seconds, 10,000 | $162.50 | $464.04 |
Every row saves 75% to 82%. Memory is most of each Sprite figure, so the saving holds however busy the CPUs are.
The calculator assumes every GB you enter is in use, so it gives Sprites' highest figure for a shape. A job that uses only 1 GB of memory in the one-minute agent run pays $0.76 per 1,000 runs on Sprites. The same 1,000 runs cost $0.64 on Runtime at 4 GiB.
What the calculator leaves out
- Plan fees. None are required for Sprites. Fly offers optional monthly plans. Runtime has no plan: prepaid credit from $10.
- Free credit. Sprites come with $30 of trial credit. Runtime gives 100 free hours of a 1 GB machine in the first 30 days, no card.
- Time awake after a run. A Sprite stays awake, and billed, for about 30 seconds after its last activity. The figures include it.
- Storage. A sleeping Sprite's disk costs $0.02 per GB a month, and its memory is dropped when it goes cold, at a time you do not choose. A paused Runtime sandbox keeps files, memory and running processes for $0.08 per GB a month, while you have credit.
Price your own runs exactly
Once you have run on Runtime, the CLI prices those sandboxes at Sprites'
published rates. The provider name fly means Sprites:
Terminalruntime compare --from flyIt prints both costs and what you save a month, from the last 30 days of
settled sandboxes, or up to 90 with --days. Credit you add within 30 days of signing up is matched, up to $1,000 in total (welcome match).
Runtime vs Fly.io covers Sprites and Machines in full. Fly's general-purpose VMs are priced by size on the Fly Machines pricing calculator. The sandbox cost calculator shows all 15 rivals side by side.
Sources
- Fly.io pricing, checked 25 October 2026
- Sprites and its pricing questions
- Runtime pricing
Rival rates on this page were checked on 25 October 2026.