TL;DR
We ran 5 real transactions on the provider testnet to empirically
verify the multi-send gas surcharge introduced in Gaia v27.0.0
(PR #3961). We confirmed the quadratic curve — and found an additional
linear component of ~8,628 gas per recipient from SDK store I/O.
Complete empirical formula: gas_total ≈ 95,302 + 8,628 × n + 300 × n²
Background
Gaia v27.0.0 introduced a quadratic gas surcharge on MsgMultiSend
to mitigate spam:
gas_surcharge = 300 × n²
We wanted to verify this in practice, so during Testnet Tuesday
(March 2026) we ran transactions with 1, 10, 20, 49, and 100
recipients on the provider testnet, recording the actual gas_used
from the public REST API.
Results
| n | gas_used (real) | Theoretical 300n² | Ratio |
|---|---|---|---|
| 1 (base) | 103,963 | — | — |
| 10 | 211,587 | 30,000 | 3.59x |
| 20 | 387,909 | 120,000 | 2.37x |
| 49 | 1,238,130 | 720,300 | 1.57x |
| 100 | 3,958,152 | 3,000,000 | 1.28x |
The ratio converges toward 1x as n grows, confirming the quadratic
term dominates at scale.
Key Finding
Beyond the documented 300 × n² surcharge, there is a consistent
linear component of ~8,628 gas per recipient representing the
Cosmos SDK store I/O cost (read account + validate balance + write
state). This slope is constant within ±0.2% across all measurements.
The complete empirical formula:
gas_total ≈ 95,302 + 8,628 × n + 300 × n²
Prediction error < 0.1% on all measured points.
Inflection point at n=29: below this threshold, the linear SDK
cost exceeds the quadratic surcharge. Above n=29, the quadratic
term dominates.
On Deterrence
Other validators also ran independent tests during Testnet Tuesday
and raised a valid point: at current ATOM prices, even 400 recipients
costs ~0.26–0.32 ATOM, which is cheap in absolute terms.
Our view: the mechanism is dynamic pricing, not a firewall. At
ATOM=$100, that same transaction costs ~$25. Scaling spam to thousands
of transactions becomes economically irrational. Near ~490 recipients,
the block gas limit (75M) rejects the transaction outright regardless
of fee — a hard ceiling.
For legitimate use cases (50–100 recipients), costs remain very
reasonable at any realistic ATOM price.
Verified Transactions
| n | TX Hash |
|---|---|
| 1 | 60886AFCE17610B5EB1E0E8E33DA84C2B7D7EBD8A7541CC5F6CAE7965A6CA873 |
| 10 | 5B704EBDD7739698BFB1F67F6CFFB12CE148B208072CD1030A988B8CFECE55E7 |
| 20 | 5CD0F241C0FF48C7D26D1AF90FCAD6F3BE9A721B592B4D5BF828E19E568F79BC |
| 49 | 499B5D156CC7447E625932A0EF63C78E49C94D7376D1D280048E82D66E8967E9 |
| 100 | A19877023233F99782AA384355649EC2F39F4F6D091163DDE0110AF8EB68FB79 |
Explorer: mintscan.io/ics-testnet-provider/tx/<HASH>
Full study with charts:
github.com/Cumulo-pro/cumulo-cosmoshub-infra/blob/main/studies/gas-surcharge-multisend-2026-03/README.md
Cumulo · Cosmos Hub Validator · Testnet Tuesday March 2026