> For the complete documentation index, see [llms.txt](https://soroban-cost-estimator.gitbook.io/soroban-cost_estimator-docs/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://soroban-cost-estimator.gitbook.io/soroban-cost_estimator-docs/resource-fees.md). # Resource Fees Every Soroban transaction pays a fee in **stroops** (1 stroop = 10⁻⁷ XLM). The fee a simulation reports is the *resource fee*: the amount the network charges for the CPU instructions, ledger I/O, transaction size, and rent your invocation implies. The RPC returns that total, but the total hides the structure. This tool splits it into two parts, using the network's own published rates. ## Non-refundable vs refundable * **Non-refundable** — the cost of the resources you *consume*: CPU instructions, ledger entries read and written, disk bytes read, and the transaction's own size. The network keeps this. It is charged regardless of what happens after the simulation. * **Refundable** — the deposit you put down for resources the network *may* need later, primarily ledger **rent** (keeping your contract's data alive) and contract events. If the data expires early or the rent liability is lower than the deposit, part of this comes back. The split matters for long-running operations: the refundable portion is what you might get back, so an estimate that lumps it into the flat fee over-states your true long-term cost. ## How the fee is computed The authoritative total comes from `simulateTransaction` (the `minResourceFee` field, which equals the `resource_fee` in the returned `SorobanTransactionData` XDR). The **non-refundable** portion is derived *independently* from the network's `ConfigSetting*` rates — never from hardcoded constants — using integer stroops math, `(units × rate) / scale`, which preserves precision better than pre-dividing the rate. The refundable portion is simply the remainder: `total − non_refundable`. | Component | Formula | Unit | | ----------- | ------------------------------------------------------------ | ------------------------------- | | CPU | `(cpu_insns × fee_rate_per_instructions_increment) / 10_000` | stroops per 10,000 instructions | | Read entry | `read_entries × fee_disk_read_ledger_entry` | stroops per ledger entry | | Write entry | `write_entries × fee_write_ledger_entry` | stroops per ledger entry | | Read bytes | `(read_bytes × fee_disk_read1_kb) / 1024` | stroops per 1 KB | | Bandwidth | `(tx_size × fee_tx_size1_kb) / 1024` | stroops per 1 KB of tx XDR | ## The real numbers The cross-check against a live deployed contract(see [Verification](/soroban-cost_estimator-docs/verification.md)) used `increment(step=5)` on testnet. The live run reported: ``` CPU instructions: 524,389 Read entries: 1 Write entries: 1 Transaction size: 156 bytes Write bytes: 136 Fee: non-refundable 4,491 stroops · refundable 12,631 stroops · total 17,122 stroops (0.0017122 XLM) ``` The fee rates come from the config snapshot taken on the same network (the full snapshot lives in `~/.soroban-cost-estimator/snapshots/` after running `config snapshot`): | Rate | Value | Source | | ------------------------------------- | ----- | ----------------------------------- | | `fee_rate_per_instructions_increment` | 7 | `ConfigSettingContractComputeV0` | | `fee_disk_read_ledger_entry` | 1,563 | `ConfigSettingContractLedgerCostV0` | | `fee_write_ledger_entry` | 2,500 | `ConfigSettingContractLedgerCostV0` | | `fee_disk_read1_kb` | 447 | `ConfigSettingContractLedgerCostV0` | | `fee_tx_size1_kb` | 406 | `ConfigSettingContractBandwidthV0` | Plug the live run's numbers into the formulas: ``` CPU fee = (524,389 × 7) / 10,000 = 367 stroops Read entry fee = 1 × 1,563 = 1,563 stroops Write entry fee= 1 × 2,500 = 2,500 stroops Read bytes fee = (0 × 447) / 1,024 = 0 stroops Bandwidth fee = (156 × 406) / 1,024 = 61 stroops Non-refundable = 367 + 1,563 + 2,500 + 61 = 4,491 stroops Refundable = 17,122 − 4,491 = 12,631 stroops ``` Both derived values match the report exactly. The refundable portion — 12,631 of the 17,122 stroops, about 74% — is dominated by the ledger rent deposit for the counter entry the contract writes, which is why this `increment` contract's *actual* long-term cost is much lower than the up-front fee. ## When a fee-rate source is missing All rates come from the network config, never from hardcoded constants. If a `ConfigSetting*` source cannot be fetched or decoded, the affected rate is set to 0 **and a warning naming the source is printed** — the non-refundable fee is then visibly understated rather than silently wrong: ``` Warning: fee rate source(s) ContractComputeV0 unavailable — affected rate(s) set to 0 (non-refundable fee understated) ``` See the [FAQ](/soroban-cost_estimator-docs/faq.md) for what this means in practice. --- # Agent Instructions This documentation is published with GitBook. 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