Canonical: https://builtonarc.app/guides/stablecoin-fx-on-arc

# Stablecoin FX on Arc: where the spread actually sits

Updated 2026-09-02. How USDC to EURC and local-currency FX works on Arc — who quotes it, where the spread sits, and AMM vs OTC vs provider conversion compared.

> Converting USDC to EURC, or either to a local currency, is a real transaction with a real cost, even though both USDC and EURC are individually stable against their reference currency — the FX exposure lives in the conversion between them, not in either stablecoin's own volatility. On Arc, that conversion can happen through an on-chain automated market maker, an OTC desk, or built into a payments provider's own conversion layer, and the three have meaningfully different spread and counterparty characteristics. Nothing described here is live on Arc mainnet yet — mainnet is 16 September 2026.

## The spread doesn't disappear just because both sides are stablecoins

It's a common misconception that converting between two dollar- and euro-pegged stablecoins should be nearly free, since neither side is a volatile asset. That's not quite right: the underlying USD/EUR exchange rate itself still moves normally, and whatever mechanism executes the conversion — an AMM pool, an OTC desk, a provider's internal ledger — still needs to price that movement and take a spread to cover its own risk and cost of providing the conversion. The stablecoin wrapper removes crypto-asset volatility from the equation; it does not remove currency-pair FX economics, which are the same economics that apply to converting USD to EUR through any other channel.

## On-chain AMM: transparent pricing, liquidity-dependent spread

An automated market maker pool pairing USDC and EURC prices the swap algorithmically based on pool composition, and the spread you actually pay is a function of pool liquidity depth and trade size relative to that depth — a small trade against a deep pool executes close to the reference rate; a large trade against a shallow pool moves the price against you meaningfully (slippage). The advantage of an AMM is transparency: the pricing mechanism and the resulting rate are visible on-chain before and after the trade, with no opaque markup hidden in a quote. The disadvantage, for a business treasury moving a meaningful size, is that on-chain liquidity for a USDC/EURC pair specifically may be shallower than what an OTC desk can offer for the same size, particularly pre-mainnet while Arc's own on-chain liquidity is still developing — check actual pool depth before assuming AMM pricing beats an alternative for your specific trade size.

## OTC desk: negotiated pricing, real counterparty relationship

An over-the-counter desk quotes a price directly for a specific size, typically with tighter effective pricing than an AMM for large trades precisely because the desk can source liquidity from multiple venues and price the risk more efficiently at scale, rather than being constrained to what's sitting in one on-chain pool. The tradeoff is that you're now in a bilateral counterparty relationship with the desk — settlement risk, credit terms, and the desk's own reputation and regulatory standing become part of the evaluation, in a way that's simply not a factor with a permissionless AMM trade. For treasury-sized conversions, ask any OTC counterparty directly about their settlement process, any pre-funding requirement, and their own licensing status — the same due-diligence standard you'd apply to any other financial counterparty.

## Provider-built conversion: convenience, at a markup you should ask about explicitly

Many payments and treasury providers bundle currency conversion directly into their product — you request a payout or settlement in a different currency than what you're holding, and the provider handles the conversion internally, whether by routing to an AMM, an OTC relationship, or their own inventory. This is the most convenient option operationally, and often the right choice for a business that doesn't want to manage FX execution directly. It's also the option where the spread is least visible by default — a bundled conversion fee can be harder to isolate than a standalone AMM or OTC quote. Ask any such provider to disclose the effective FX spread explicitly, separate from any stated transaction fee.

## Local-currency legs: usually a provider or OTC problem, rarely an AMM one

Converting USDC or EURC to a local currency outside the major pairs — Nigerian naira, Philippine peso, and similar — generally lacks meaningful on-chain AMM liquidity; this leg almost always runs through a licensed provider or OTC relationship with actual local-currency banking rails, looping back to the licensing question in Built on Arc's <a href="/cross-border-remittances-on-arc">remittances guide</a>. Don't expect AMM-style on-chain pricing for a local-currency leg the way you might for a major pair like USDC/EURC.

## What to actually ask before executing a conversion

Concretely: what's the effective spread versus the reference exchange rate, at your actual trade size (not a headline "0% fee" that excludes the spread); is the counterparty an AMM, an OTC desk, or a provider routing to one of those; and for any local-currency leg, is the counterparty actually licensed to handle that currency's on/off-ramp. Built on Arc's <a href="/eurc-on-arc">EURC guide</a> covers EURC specifically, including its regulatory status; Built on Arc's <a href="/usdc-vs-eurc-on-arc-for-business">USDC vs EURC guide</a> covers the broader currency-of-settlement decision for a business.

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Built on Arc is an independent directory. Arc is a Circle product; we are not affiliated with, endorsed by, or operated by Circle.



Sources:
- [Circle Announces Founding Validator Cohort and Major Integrations for Arc](https://www.circle.com/pressroom/circle-announces-founding-validator-cohort-and-major-integrations-for-arc-ahead-of-september-16-mainnet-launch)
- [Arc Docs — contract addresses](https://docs.arc.io/arc/references/contract-addresses)
- [Arc | The Economic OS — official site](https://www.arc.io/)

## Questions

**Is converting USDC to EURC free since both are stablecoins?**

No — the underlying USD/EUR exchange rate still moves, and whatever executes the conversion (AMM, OTC desk, or provider) prices that movement and takes a spread. Stablecoin status removes crypto-asset volatility, not currency-pair FX economics.

**Is an AMM or an OTC desk cheaper for converting USDC to EURC?**

It depends on trade size. Small trades against deep liquidity often price close to the reference rate on an AMM; large trades typically get tighter effective pricing from an OTC desk that can source liquidity across venues rather than being limited to one on-chain pool.

**What's the risk difference between AMM and OTC conversion?**

An AMM trade is permissionless with transparent on-chain pricing and minimal counterparty relationship. An OTC trade involves a real bilateral counterparty — settlement risk, credit terms, and the desk's licensing status all become relevant.

**Can I convert USDC directly to any local currency on-chain?**

Generally not with meaningful AMM liquidity for most local currencies — that leg typically runs through a licensed provider or OTC relationship with actual local banking rails, not an on-chain pool.

**Is any of this live on Arc yet?**

No — Arc mainnet launches 16 September 2026, and on-chain liquidity specifically for Arc-based pairs is still developing pre-mainnet. Evaluate conversion options now on Arc testnet where possible, ahead of any live volume.