> ## Documentation Index
> Fetch the complete documentation index at: https://docs.ton.org/llms.txt
> Use this file to discover all available pages before exploring further.
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# Gas
Each instruction executed in TVM consumes gas. All instructions consume *basic gas*, which is calculated from the size of the instruction in the bitcode. Some instructions may consume *extra gas*, which is often not fixed but calculated based on the input data.
## Basic gas usage (per bit of executed code)
Each instruction consumes a fixed amount of `10` gas and `1` gas for each bit of this instruction, not including variable-length operands and references.
Examples:
| Instruction | TL-B | Gas | Notes |
| ------------------------------------------------------- | ------------------------------------------------------------------------------------------------ | ---- | -------------------------------------------------------------------------------------------------------------------------------------------------- |
| [`NEWC`](/tvm/instructions#c8-newc) | `#C8` | `18` | 8-bit prefix without operands |
| [`STU`](/tvm/instructions#cb-stu) | `#CB`
`cc:uint8` | `26` | 8-bit prefix, 8-bit operand |
| [`PUSHINT_LONG`](/tvm/instructions#82-pushint_long) | `#82`
`l:(## 5)`
`xxx:(int (8 * l + 19))` | `23` | 8-bit prefix, 5-bit operand, length of `xxx` depends on `l`, so it is not included |
| [`STSLICE_CONST`](/tvm/instructions#cfc0_-stsliceconst) | `#CFC0_`
`x:(## 2)`
`y:(## 3)`
`c:(x * ^Cell)`
`sss:((8 * y + 2) * Bit)` | `24` | 9-bit prefix (`CF` is 8 bits, `C0_` is `C_`, which is just bit `1`), 2-bit and 3-bit operands, refs `c` and variable-length `sss` are not included |
## Cell operations
When any instruction internally finalizes a `Builder` to a `Cell`, it consumes `500` gas. When a `Cell` is loaded as a `Slice`, it consumes `100` gas for the first access in current smart contract invocation, and `25` gas for each subsequent load from cache. Cells are identified by representation hash, e.g., loading cell with the same hash for the second time will always cost `25` gas.
This applies to all instructions that internally operate with cells (including dictionary operations). The only exceptions are:
* `BTOS` converts a `Builder` to a `Slice` without consuming gas for cell operations.
* `HASHBU` computes hash without consuming gas for converting `Builder` to a `Cell`
## Exceptions
TVM consumes `50` gas when any exception is thrown, both explicitly by [`THROW`](/tvm/instructions#f2c4_-throw)-like instructions or implicitly during execution of other instructions. This happens before the jump to the exception handler `c2`.
## Implicit jumps and returns
When the current continuation ends and there is a remaining reference, TVM jumps to it and consumes `10` gas. When there are no instructions to execute and references to jump to, implicit return to `c0` occurs, which consumes `5` gas.
## Nested continuations
Calling more than `8` extraordinary continuations in a chain consumes `1` gas for each subsequent continuation.
## Tuple operations
[`TUPLE`](/tvm/instructions#6f0-tuple), [`TUPLEVAR`](/tvm/instructions#6f80-tuplevar), [`UNTUPLE`](/tvm/instructions#6f2-untuple), [`UNTUPLEVAR`](/tvm/instructions#6f82-untuplevar), [`UNPACKFIRST`](/tvm/instructions#6f3-unpackfirst), [`UNPACKFIRSTVAR`](/tvm/instructions#6f83-unpackfirstvar), [`EXPLODE`](/tvm/instructions#6f4-explode), [`EXPLODEVAR`](/tvm/instructions#6f84-explodevar) consumes `1` gas for each entry been pushed or popped into a tuple. [`TPUSH`](/tvm/instructions#6f8c-tpush), [`TPOP`](/tvm/instructions#6f8d-tpop), [`SETINDEX`](/tvm/instructions#6f5-setindex), [`SETINDEXVAR`](/tvm/instructions#6f85-setindexvar), [`SETINDEXQ`](/tvm/instructions#6f7-setindexq)/[`SETINDEXVARQ`](/tvm/instructions#6f87-setindexvarq) consumes `len(tuple)` gas for the resulting tuple size after push/pop/set. Same applies to instructions operating with `c7`: [`SETGLOB`](/tvm/instructions#f87_-setglob)/[`SETGLOBVAR`](/tvm/instructions#f860-setglobvar), [`RANDU256`](/tvm/instructions#f810-randu256)/[`RAND`](/tvm/instructions#f811-rand), [`SETRAND`](/tvm/instructions#f814-setrand), [`ADDRAND`](/tvm/instructions#f815-addrand).
## Stack operations
TVM consumes 1 gas for each stack element deeper than 32 elements inside the resulting new stack each time stack gets copied: when calling or jumping to a continuation with a non-empty argument number, an initial stack, or both, when extending a continuation stack using [`SETCONTARGS`](/tvm/instructions#ec-setcontargs_n) and similar instructions, when using [`RUNVM`](/tvm/instructions#db4-runvm) (both for initial and resulting stacks of the vm).
## Extra currency
The first `5` executions of `GETEXTRABALANCE` consume at most `26 + 200` gas each. The subsequent executions incur the full gas cost of `26` (normal instruction cost) plus gas for loading cells (up to `3300` if the dictionary has maximum depth).
## RUNVM
[`RUNVM`](/tvm/instructions#db4-runvm) and [`RUNVMX`](/tvm/instructions#db50-runvmx) consume `40` extra gas before starting a VM.
## Cryptography
### CHKSIGNS/CHKSIGNU
[`CHKSIGNS`](/tvm/instructions#f911-chksigns) and [`CHKSIGNU`](/tvm/instructions#f910-chksignu) can be invoked `10` times without extra gas cost. Next checks will cost `4000` gas each.
### HASHEXT
`HASHEXT*` instructions always consume `1` extra gas for each part of the input. Additionally, the following gas is consumed for each hashed byte:
| Algorithm | Gas consumed |
| --------- | ------------- |
| SHA256 | 1/33 per byte |
| SHA512 | 1/16 per byte |
| BLAKE2B | 1/19 per byte |
| KECCAK256 | 1/11 per byte |
| KECCAK512 | 1/6 per byte |
Only the integer part of the gas is consumed; for example, 0-32 bytes of SHA256 cost 0 gas, 33-64 bytes cost 1 gas, and so on.
### RIST255
Instructions consume constant extra gas.
| Instruction | Extra gas |
| ------------------------------------------------------------- | --------- |
| [`RIST255_FROMHASH`](/tvm/instructions#f920-rist255_fromhash) | 600 |
| [`RIST255_VALIDATE`](/tvm/instructions#f921-rist255_validate) | 200 |
| [`RIST255_ADD`](/tvm/instructions#f922-rist255_add) | 600 |
| [`RIST255_MUL`](/tvm/instructions#f924-rist255_mul) | 2000 |
| [`RIST255_MULBASE`](/tvm/instructions#f925-rist255_mulbase) | 750 |
### Other instructions
[`ECRECOVER`](/tvm/instructions#f912-ecrecover) consumes 1500 extra gas.
`SECP256K1_XONLY_PUBKEY_TWEAK_ADD` consumes 1250 extra gas.
[`P256_CHKSIGNU`](/tvm/instructions#f914-p256_chksignu) and [`P256_CHKSIGNS`](/tvm/instructions#f915-p256_chksigns) consume 3500 extra gas.
### BLS
#### Signature verification and aggregation
| Instruction | Gas consumed | Notes |
| ----------------------------------------------------------------------------- | ------------------- | --------------------------------------------------------------------------------- |
| [`BLS_VERIFY`](/tvm/instructions#f93000-bls_verify) | `61000` | |
| [`BLS_AGGREGATE`](/tvm/instructions#f93001-bls_aggregate) | `-2650 + 4350 * n` | `n` is the number of signatures aggregated. |
| [`BLS_FASTAGGREGATEVERIFY`](/tvm/instructions#f93002-bls_fastaggregateverify) | `58000 + 3000 * n` | `n` is the number of public keys verified against one message/signature pair. |
| [`BLS_AGGREGATEVERIFY`](/tvm/instructions#f93003-bls_aggregateverify) | `38500 + 22500 * n` | `n` is the number of `(public key, message)` pairs checked against one signature. |
#### G1 group helpers
| Instruction | Gas consumed |
| --------------------------------------------------------------------------------------------------------- | ------------ |
| [`BLS_G1_ADD`](/tvm/instructions#f93010-bls_g1_add) / [`BLS_G1_SUB`](/tvm/instructions#f93011-bls_g1_sub) | `3900` |
| [`BLS_G1_NEG`](/tvm/instructions#f93012-bls_g1_neg) | `750` |
| [`BLS_G1_MUL`](/tvm/instructions#f93013-bls_g1_mul) | `5200` |
| [`BLS_MAP_TO_G1`](/tvm/instructions#f93016-bls_map_to_g1) | `2350` |
| [`BLS_G1_INGROUP`](/tvm/instructions#f93017-bls_g1_ingroup) | `2950` |
[`BLS_G1_MULTIEXP`](/tvm/instructions#f93014-bls_g1_multiexp) consumes `11375 + 630 * n + (8820 * n) / max(log₂ n, 4)` extra gas, where `n` is the number of `(point, scalar)` pairs.
Instructions [`BLS_G1_ZERO`](/tvm/instructions#f93015-bls_g1_zero) and [`BLS_G1_ISZERO`](/tvm/instructions#f93018-bls_g1_iszero) do not charge additional gas.
#### G2 group helpers
| Instruction | Gas consumed |
| --------------------------------------------------------------------------------------------------------- | ------------ |
| [`BLS_G2_ADD`](/tvm/instructions#f93020-bls_g2_add) / [`BLS_G2_SUB`](/tvm/instructions#f93021-bls_g2_sub) | `6100` |
| [`BLS_G2_NEG`](/tvm/instructions#f93022-bls_g2_neg) | `1550` |
| [`BLS_G2_MUL`](/tvm/instructions#f93023-bls_g2_mul) | `10550` |
| [`BLS_MAP_TO_G2`](/tvm/instructions#f93026-bls_map_to_g2) | `7950` |
| [`BLS_G2_INGROUP`](/tvm/instructions#f93027-bls_g2_ingroup) | `4250` |
[`BLS_G2_MULTIEXP`](/tvm/instructions#f93024-bls_g2_multiexp) consumes `30388 + 1280 * n + (22840 * n) / max(log₂ n, 4)` gas, where `n` is the number of `(point, scalar)` pairs.
Instructions [`BLS_G2_ZERO`](/tvm/instructions#f93025-bls_g2_zero) and [`BLS_G2_ISZERO`](/tvm/instructions#f93028-bls_g2_iszero) do not charge additional gas.
#### Pairing and constants
| Instruction | Gas consumed | Notes |
| ----------------------------------------------------- | ------------------- | ----------------------------------------------------------------------------- |
| [`BLS_PAIRING`](/tvm/instructions#f93030-bls_pairing) | `20000 + 11800 * n` | `n` is the number of `(G1, G2)` pairs supplied for the pairing product check. |
[`BLS_PUSHR`](/tvm/instructions#f93031-bls_pushr) do not charge additional gas.
## `GasLimits` structure
TVM has inner structure `GasLimits` for gas manipulations. Its fields are:
* `gas_max`: the equivalent of contract's balance at the start of the compute phase in gas units.
* `gas_limit`: the amount of gas that can be consumed during the virtual machine execution. At the start of the execution, it equals:
* minimum of `gas_max` and the amount of gas that can be bought with the incoming message value (i.e., the amount of TON coins attached to the message) in the case of an internal message;
* `0` in the case of an external message.
* `gas_credit`: the amount of free gas that can be spent during the execution before accepting an external message. At the start of the execution, it equals:
* minimum of `gas_max` and corresponding value in configuration parameter `20` for masterchain and `21` for basechain in the case of an external message;
* `0` in the case of an internal message.
* `gas_remaining`: the amount of available but not spent gas. At the start of the execution, it equals `gas_limit + gas_credit`. It decreases after each instruction execution by the amount of gas consumed by the instruction.
* `gas_base`: an auxiliary parameter that is necessary for rebasing and shows the initial value of `gas_remaining`. At the start of the execution, it equals `gas_remaining`.
Instructions `SETGASLIMIT` and `ACCEPT` change all above values except `gas_max`:
* `SETGASLIMIT` sets `gas_limit` to the minimum of the indicated value and `gas_max`, `gas_credit` to zero, `gas_base` to the new `gas_limit`, and `gas_remaining` to `gas_remaining + (new gas_base - old gas_base)`.
* `ACCEPT` is equivalent to `SETGASLIMIT` with the new gas limit equal to `2**63 - 1` (the maximum value of a signed 64-bits integer).
The final value (in gas units) that will be deducted from contract's balance after the execution is `gas_base - gas_remaining`. Note that this value will be deducted if and only if after the execution `gas_credit` is zero, i.e. if `SETGASLIMIT` or `ACCEPT` was called at least once during the execution in the case of incoming external message. Without condition `gas_credit == 0`, there will be no commit of the new code and data.