Fly Sprites pricing calculator: what your sandboxes cost, and on Runtime

Fly Sprites bill $0.07 per CPU-hour of measured CPU and $0.04375 per GB-hour of memory in use, with no plan required.

Runtime costs 81% 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 $330.56 on Sprites. Both bill measured CPU, and both run Firecracker microVMs; Runtime's rates are lower on each meter. Rates checked 23 September 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, and Fly manages how much that is, so it is not a figure you set.

Meter	Fly Sprites	Runtime
CPU	$0.07 per CPU-hour, measured	$0.025 per vCPU-hour, measured, floor 0.05 of a vCPU
Memory	$0.04375 per GB-hour of memory in use	$0.0075 per reserved GiB-hour

Runtime's CPU rate is about a third of Sprites' and its memory rate about a sixth. 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 $0.175 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	$330.56
Every CPU busy: 2 vCPU, 4 GiB, 60 s, 120 CPU-seconds, 100,000	$133.33	$525.00
Tool calls: 1 vCPU, 2 GiB, 2 min, 30 CPU-seconds, 50,000	$35.42	$175.00
Waiting agents: 2 vCPU, 4 GiB, 30 min, 180 CPU-seconds, 10,000	$162.50	$910.00

Every row saves 75% to 82%. Memory is most of each Sprite figure, so the saving holds however busy the CPUs are.

Because the calculator assumes every GB you enter is in use, it gives Sprites' highest figure for a shape. A job that uses only 1 GB of memory in the one-minute agent run pays $1.12 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 50 sandbox hours on the free trial, no card.
• Time awake after a run. A Sprite stays awake for about 30 seconds after its last activity unless you delete it. The figures assume it stops when the run ends.
• 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, for the 1 to 365 days you set.

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 fly

It prints both costs and what you save a month, from the last 30 days of settled sandboxes, or up to 90 with --days. runtime switch --from fly before your first top-up gets that top-up matched, up to $100 (switching credit).

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, and the sandbox cost calculator shows all 12 rivals at once.

Sources

• Fly.io pricing, checked 23 September 2026
• Sprites and its pricing questions
• Runtime pricing

Rival rates on this page were checked on 23 September 2026.