The Auton Currency Unit (ACU) was Autonity's basket-pegged reference currency. It tracked a fixed-quantity basket of seven major currencies using the same methodology the IMF uses for the Special Drawing Right (SDR): fixed amounts, floating daily weights.
ACU was a design reference for USDZ, the AFP's primary settlement token. The basket mechanic is presented here for educational record. Not financial advice.
The IMF's Special Drawing Right (SDR) is the canonical basket currency. Its value is computed daily by multiplying each constituent currency's fixed amount by that currency's USD exchange rate, then summing. The basket amounts are set by the IMF every five years; the weights drift daily as exchange rates move.
Autonity adopted exactly this methodology for the ACU. Seven currencies received fixed amounts at basket inception. Each day, the ACU index value in USD was computed as the sum of (fixed amount × USD rate) across all seven currencies. Each currency's weight at any moment was its contribution to that sum — not a fixed target.
If you fix a currency's weight (say, "EUR = 30% of the basket"), you have to rebalance the basket every day as exchange rates move. This requires a transaction, a cost, and a discretionary choice. If you fix the amount (say, "EUR = 0.143 in the basket"), no rebalancing is ever needed — the weight simply drifts. The SDR has used this method since 1974. Autonity's ACU uses it for the same reason: the basket is stable by construction, not by intervention.
The ACU basket used amounts specified at scale 105 (i.e., divide by 100,000 for the actual amount per unit of ACU). The seven constituents and their fixed amounts were:
| Currency | Code | Amount (raw ×105) | Actual Amount | Basis |
|---|---|---|---|---|
| AUD Australian Dollar | AUD | 21,300 | 0.21300 | G10 trade weight |
| CAD Canadian Dollar | CAD | 18,700 | 0.18700 | G10 trade weight |
| EUR Euro | EUR | 14,300 | 0.14300 | SDR EUR component |
| GBP British Pound | GBP | 10,400 | 0.10400 | SDR GBP component |
| JPY Japanese Yen | JPY | 1,760,000 | 17.60000 | SDR JPY component |
| USD US Dollar | USD | 18,000 | 0.18000 | SDR USD component |
| SEK Swedish Krona | SEK | 141,000 | 1.41000 | Nordic inclusion |
JPY has a much larger raw amount because the yen is denominated in small units per dollar. The actual USD contribution from JPY is comparable to the other currencies once multiplied by the USD/JPY exchange rate.
Enter today's USD rates for each currency. The calculator derives the ACU index value and the floating weight of each constituent. Use the presets to see how rate movements shift weights.
The IMF SDR basket currently contains five currencies: USD, EUR, CNY, JPY, GBP. Weights are recomputed daily from fixed amounts — exactly the ACU method. The SDR basket composition is reviewed and reset every five years (last reset: August 2022). The ACU basket added AUD, CAD, and SEK; it excluded CNY.
Multi-currency basket stablecoins remain an active research area. The BIS Innovation Hub, Project mBridge, and several CBDC interoperability proposals have explored basket structures similar to the ACU. None have shipped at production scale yet. The ACU was a working testbed.
IMF SDR — 5-currency basket, recomputed daily, used for IMF lending and reserve accounting. Project mBridge mCBDC — multi-CBDC bridge that explored basket settlement. Libra / Diem (2019–2022) — Facebook's proposed multi-currency basket stablecoin; abandoned under regulatory pressure. The ACU predated all of these as a live on-chain implementation.