Paying for resources in cycles

Beginner

Concept

Overview

Canister smart contracts pay for consumed resources (storage, messaging, execution, and special features) by burning cycles. Developers can obtain cycles by converting ICP tokens into cycles using dfx.

For pricing estimations, you can use the pricing calculator.

This page will provide details about how costs are calculated.

The reverse gas model

ICP charges each canister smart contract for the resources that it consumes. It's the developer's responsibility to load each of their canisters with adequate cycles to pay for these resources. This cost model is known as ICP's reverse gas model.

The reverse gas model allows dapp developers to provide their users a smooth experience, since end users don't need to obtain tokens, configure wallets, or sign and approve every transaction they perform when interacting with a dapp on ICP.

You can learn more about the reverse gas model.

One downside of the ICP reverse gas model is that it requires prerequisite steps and ongoing maintenance for developers. Canisters must have their cycles balances maintained and regularly topped up as they continuously use resources. The canister will be removed from the network if it runs out of cycles.

Learn how to query a canister's cycles balance.

Learn how to top up a canister.

A freezing threshold can be set that pauses a canister's executions if the cycles amount is expected to fall below a certain amount. There are several community tools that have been developed to automate managing a canister's cycles, such as CycleOps.

Units and fiat value

The price of cycles is fixed against the price of XDR, where 1 trillion cycles equals 1 XDR. As of December 18, 2023, the exchange rate for 1 XDR = $1.336610. The exchange rate for USD/XDR may vary. Learn more about XDR exchange rates.

The following table shows units of cycles and the respective fiat values:

Abbreviation	Name	In numbers	Cycles XDR value	Cycles USD value
T	Trillion	1_000_000_000_000	1	1.336610
B	Billion	1_000_000_000	0.001	0.001336610
M	Million	1_000_000	0.000001	0.000001336610
k	Thousand	1_000	0.000000001	0.000000001336610

Replication

When a canister is deployed to a subnet, it is automatically replicated on every node within that subnet. The amount of cycles that a canister is charged will vary based on the amount of times the canister is replicated:

• Canisters deployed locally are deployed on a single node and therefore are replicated once. Cycles charged to locally deployed canisters have a cost that is 1 / 13 the cost when deployed to a 13-node subnet. In local development environments, cycles can be fabricated using dfx.

• Canisters deployed to a 13-node subnet are replicated 13 times. Cycle cost amounts are based on a 13-node subnet, i.e., there is no calculation needed to determine the cost based on the subnet's replication factor.

• Canisters deployed to a 34-node subnet are replicated 34 times. If you intend to deploy canisters on high-replication subnets (greater than 13 nodes), your canister should be prepared for an increase in cycles prices. Calls made to high-replication subnets will also require more cycles. Cycles costs on 34-node subnets can be calculated as cost / 13 * 34.

Cost details: canister operations and resources

Canisters are charged for the resources they consume and any operations they perform using features such as HTTPS outcalls, ECDSA signing, and the Bitcoin integration API. At a high level this can be visualized using the following diagram:

Each type of canister operation and resource has a different cycles cost associated with it. The canister responsible for paying the cycles varies based on the type of operation.

The following subsections explain the pricing for the different operation and resource types for a canister deployed on a 13 node subnet. The same operations and resources cost linearly more on subnets with more nodes.

Canister creation

Canister creation costs 100B cycles or approximately $0.13 USD. Canisters can be created by users or other canisters.

Messaging

A canister can receive messages from users and other canisters. In canister-to-canister messages, the sending canister pays the message transmission costs. In user-to-canister messages, the receiving canister covers the message transmission costs. User-to-canister messages are also referred to as ingress messages.

The current fees are:

Message type	Base fee	Per byte fee
Query call	0	0
Canister-to-canister	260K	1K
User-to-canister (ingress)	1.2M	2K

View the cost calculation formula for more information about how costs are calculated.

Note that query messages are currently free, but this may change in the future.

Execution and compute allocation

To handle an incoming message or task such as a timer or heartbeat, the canister executes the function specified in the message.

By default, canisters are scheduled for execution in a "best-effort" manner. Canisters that require guaranteed execution can get a share of compute capacity by setting compute_allocation in their canister settings. Compute allocation is expressed in percents and denotes the percentage of an execution core reserved for the canister.

Setting even 1% compute allocation provides a significant advantage over canisters that use the "best-effort" scheduling:

• For 1% compute allocation, the canister will receive 1% of an execution core and is guaranteed to be scheduled every 100 rounds (assuming it executes only non-DTS messages).

• For 2% compute allocation, the canister will receive 2% of an execution core and is guaranteed to be scheduled every 50 rounds.

• For 50% compute allocation, the canister will receive 50% of an execution core and is guaranteed to be scheduled every other round.

• For 100% compute allocation, the canister will receive 100% of an execution core and is guaranteed to be scheduled every round.

The allocatable compute capacity is 299% per subnet. Compute allocation is guaranteed if it is configured.

Compute is a finite resource and is priced as such. The current fee for 1% compute allocation per second is 10M cycles (or $0.0000133661 USD). Therefore, a canister that requests 100% compute allocation would be charged 10M * 100 cycles per second.

View the cost calculation formula for more information about how costs are calculated.

Storage

Canisters pay for storage consumed by their Wasm memory and stable memory per time. Storing 1 GiB for 1 second costs 127k cycles, which amounts to ~4T cycles (or $5.35 USD) for storing 1 GiB for 1 year.

Canisters can reserve storage on a subnet through the memory_allocation setting. However, the canister will be charged as if the entire amount of allocated storage is being used.

Resource reservation mechanism

In order to encourage long-term usage and discourage spiky usage patterns, the Internet Computer uses a resource reservation mechanism that was adopted by the community in NNS proposal 12604.

When a canister allocates new storage bytes, the system sets aside some number of cycles from the main balance of the canister that are used to cover future payments for the newly allocated bytes. The reserved cycles are not transferable, and the number of reserved cycles depends on how full the subnet is. It may cover days, months, or even years of payments.

The operations that allocate new bytes are:

• Wasm instruction: memory.grow.
• System API calls: ic0.stable_grow() ic0.stable64_grow().
• Increasing the memory_allocation in canister settings.

These operations reserve some cycles by moving them from the main balance of the canister to the reserved cycles balance. The amount of reserved cycles depends on how many bytes are allocated and on the current subnet usage.

• If subnet usage is below 450GiB, then the amount of reserved cycles per allocated byte is 0.
• If subnet usage is above 450GiB, then the amount of reserved cycles per allocated byte grows linearly depending on the subnet usage, from 0 to 10 years worth of storage payments at the subnet capacity (which is currently 750GiB).

A controller of a canister can disable resource reservation by setting the reserved_cycles_limit=0 in canister settings. Such opted-out canisters would not be able to allocate if the subnet usage is above 450GiB.

Special features

Special features have different costs since they use special infrastructure to provide the feature's functionality. These special features include:

• HTTPS outcalls: These costs are included in the chart found below. View the cost calculation formula for more information about how this cost is calculated.

• Bitcoin API: Pricing for the Bitcoin API is available in the Bitcoin API documentation.

• Chain-key signing API: Pricing for the threshold signatures, such as threshold ECDSA and threshold Schnorr, is available in the threshold signatures documentation.

• EVM RPC Pricing for the EVM RPC canister is available in the EVM RPC canister documentation.

Who is responsible for paying cycles?

Canisters are responsible for paying cycles for their own canister creation, compute resources, storage resources, and execution resources. For certain canister calls, the canister responsible for paying the cycles may vary.

• Ingress messages: The receiving canister is responsible for paying.
• Inter-canister calls: Each canister pays for the calls that it sends.
• Local processing: Each canister pays for local processing.
• Child canisters: Responsible for paying for themselves.

Cycles price breakdown

The table below details the cost of compute, storage transmissions and canister calls.

You can use the pricing calculator to estimate the cost for your dapp.

Canister transmission	Description	Who is responsible for paying the cycles fee?	13-node subnets cycles cost	13-node subnets USD cost	34-node subnets	34-node subnets USD cost
Query call		Query information from a canister.	N/A	Free	Free	Free	Free
Canister creation	For creating canisters on a subnet.	Created canister	100B	$0.133661000000	100B / 13 * 34	$0.349574923077
Compute percent allocated per second	For each percent of the reserved compute allocation (a scarce resource).	Canister with allocation	10M	$0.000013366100	10M / 13 * 34	$0.000034957492
Update message execution	For every update message executed.	Target canister	590K	$0.000000788600	590K / 13 * 34	$0.000002062492
1B executed instructions	For every 1B instructions executed when executing update type messages.	Canister executing instructions	400M	$0.000534644000	400M / 13 * 34	$0.001398299692
Xnet call	For every inter-canister call performed (includes the cost for sending the request and receiving the response).	Sending canister	260K	$0.000000347519	260K / 13 * 34	$0.000000908895
Xnet byte transmission	For every byte sent in an inter-canister call (for bytes sent in the request and response).	Sending canister	1K	$0.000000001337	1K / 13 * 34	$0.000000003496
Ingress message reception	For every ingress message received.	Receiving canister	1.2M	$0.000001603932	1.2M / 13 * 34	$0.000004194899
Ingress byte reception	For every byte received in an ingress message.	Receiving canister	2K	$0.000000002673	2K / 13 * 34	$0.000000006991
GiB storage per second	For storing a GiB of data per second.	Canister with storage	127K	$0.000000169749	127K / 13 * 34	$0.000000443960
HTTPS outcalls
HTTPS outcall (per call)	For sending an HTTPS outcall to a server outside the IC, per message (http_request).	Sending canister	49_140_000	$0.000065681015	171_360_000	$0.000229041490
HTTPS outcall request message size (per byte)	For sending an HTTPS outcall to a server outside the IC, per request byte (http_request).	Sending canister	5_200	$0.000000006950	13_600	$0.000000018178
HTTPS outcall response message size (per byte)	For sending an HTTPS outcall to a server outside the IC, per reserved response byte (http_request).	Sending canister	10_400	$0.000000013901	27_200	$0.000000036356

The following table shows the calculated storage cost per GiB for a 30-day month:

		13-node subnets	34-node subnets
GiB Storage Per Month	For storing a GiB of data per month	$0.446150495	$1.70

Cost calculation formulas

A detailed, mathematical example of how the cost of running a canister on a 13-node subnet is computed can be found on the wiki.

Specific mathematical formulas used for different types of costs can be found below for reference.

Message transmissions

A fixed baseline fee and per-byte-fee charged for each byte of the message: base-fee + per-byte-fee * size-in-bytes.

Execution

The execution cost consists of a fixed execution fee and per-instruction fee (on application subnets (13 nodes), 10 instructions cost 4 cycles) that is charged for each executed WebAssembly instruction:

base-fee + per-instruction-fee * number-of-instructions

The current values of fees are base-fee = 590K cycles (or $0.0000007885999 USD), per-instruction-fee = 0.4 cycles (or $0.0053 USD for 1B instructions).

HTTPS outcalls

The cost for an HTTPS outcall is calculated using the formula (3_000_000 + 60_000 * n) * n for the base fee and 400 * n each request byte and 800 * n for each response byte, where n is the number of nodes in the subnet.

Errors related to cycles

Common errors related to cycles include:

• Insufficient cycles in memory grow.
• Reserved cycles limit exceeded in memory grow.
• Insufficient cycles in message memory grow.
• Insufficient cycles in compute allocation.
• Insufficient cycles in memory allocation.
• Insufficient cycles in memory grow.
• Reserved cycles limit exceeded in memory allocation.
• Install code not enough cycles.
• Create canister not enough cycles.

Further readings

Monitoring cycles usage

• Check your canister's cycles balance.
• Monitor your canister's cycles usage.
• Motoko cycles management library.

Getting cycles back from a canister

• To withdraw cycles from a canister, the canister must be deleted.

Topping up canisters

• Top up your canisters.
• Cycles management services.
• Cycle.express.

Counting instructions

• Motoko function countInstructions.
• IC interface specification.