A stablecoin yield calculator that returns a useful number has to do six things. Convert APR to APY using the actual compounding frequency. Strip native token incentives from real yield. Net out platform fees, withdrawal fees, and management cuts. Amortize gas across the deposit lifetime. Adjust for the holding period. Apply a tax rate appropriate to the jurisdiction. Most front-end APY badges skip four of those six steps. This guide walks through each input and ends with a $10K deposit comparison across Aave, Morpho, Sky and Coinbase, with every rate pulled on September 16 2026.
​

The six inputs that turn quoted APY into net yield:

APR is the headline rate without compounding. APY is APR after compounding is applied. The formula is APY = (1 + APR/n)^n - 1, where n is the number of compounding periods per year. For an APR of 5.00% compounded daily, n = 365, and APY = 5.127%. Compounded per block (12-second blocks on Ethereum, so a bit over two and a half million blocks a year), the same rate converges on the continuous-compounding limit, e^0.05 - 1 = 5.127%. Both figures are outputs of the formula above, not observed rates.
​

The practical takeaway: above daily compounding, the APR-to-APY gap is nearly constant. The interesting differences come from protocols that pay rates as APY directly (Sky's savings rate showed 3.60% APY on sUSDS on September 16 2026 per DeFiLlama, already compounded) versus protocols that quote APR (some Curve and Convex pools display APR, requiring conversion). Always check which one the front-end is showing. Aave and Morpho dashboards quote APY by default; many liquidity-mining dashboards quote APR for the reward token and APY for the underlying.
​

Three compounding cadences show up in stablecoin yield. Per-block compounding (Aave V3, Morpho Blue) accrues interest into the receipt token every Ethereum block, roughly every 12 seconds. Per-second compounding (Sky's Savings Rate, Spark) updates a rate accumulator each second; depositors see balance growth on demand. Per-epoch compounding (Ethena sUSDe) accrues yield over an 8-hour funding epoch and distributes at the epoch boundary.
​

For sub-daily compounding, the APY converges to e^APR - 1. At an APR of 5%, that is an APY of 5.127%. At 10%, 10.517%. At 20%, 22.140%. The longer the gap between compounding events, the lower the effective APY: at an APR of 5%, daily compounding gives 5.127%, weekly 5.125%, monthly 5.116%. These are all outputs of the compounding formula, not quoted market rates. The takeaway is that compounding frequency matters most at high rates. At single-digit yields the gap between hourly and daily compounding is smaller than a single basis point. At triple-digit emissions APRs on incentive pools, compounding frequency moves the answer meaningfully.
​

Real yield is paid in the deposit asset by another protocol user. A USDC supplier on Aave earns USDC interest paid by a USDC borrower. Real yield does not require selling a token to capture; the depositor can hold USDC throughout. Native yield is paid in the protocol's emissions token (CRV, BAL, AAVE, MORPHO, COMP, etc.) and is only realized when that token is sold for USDC. If the emissions token drops 30% between accrual and sale, 30% of the headline APR evaporates.
​

A pool whose headline rate is mostly emissions is not the same product as a pool paying the same headline entirely from borrower demand. DeFiLlama splits the two for most pools as base APY and reward APY, which is the split to check before comparing anything. Treat the reward portion at a discount reflecting expected sell pressure; there is no published industry figure for what that discount should be, so pick one and apply it consistently. For Sky's SSR, Aave V3 USDC, Morpho Blue USDC vaults (without rewards), and Coinbase USDC rewards, the entire quoted rate is real yield in USDC terms. For yield-farming pools on Curve, Convex, Velodrome, Aerodrome, and similar venues, the emissions portion is usually the majority of the rate. See the companion piece on risks of yield-bearing stablecoins for why even "real" yield can carry hidden risk.
​

Three fee buckets show up in onchain stablecoin yield. Protocol reserve factor: Aave V3 takes 10-25% of borrower interest as a reserve, and the published supply APY already nets this out, so no further adjustment is needed for Aave or Morpho. Vault performance fees: MetaMorpho vaults on Morpho commonly charge a 10-15% performance fee to the curator, taken at withdrawal, and the displayed APY may or may not net this out depending on which front-end is read. Withdrawal fees: some yield-bearing tokens (older Yearn vaults, certain Beefy strategies) charge a small withdrawal fee, typically 0.1-0.5%, to discourage rapid in-and-out cycling.
​

Exchange-side products have their own fee stack. Coinbase USDC rewards quoted 3.50% APY on September 16 2026, available only to Coinbase One members on plans starting at $4.99 per month, per Coinbase's USDC page. The rate is net of Coinbase's spread, since Coinbase keeps the difference between what it earns and what it pays. A centralized exchange that quotes a high stablecoin rate may be earning 8% and paying out 4%, keeping the rest as a margin. That structure is transparent on Coinbase (the gap is the entire business model) but opaque on smaller exchanges. The number to compare is always net yield to the depositor.
​

Gas is fixed-cost; the deposit is variable, so the drag scales with the gas price and inversely with deposit size. At the 0.078 gwei base fee prevailing on September 16 2026, Etherscan's gas tracker prices a lending-protocol interaction at about $0.06, so an entry plus an exit is roughly $0.11 and the drag on a $10,000 deposit is well under a basis point. The arithmetic only bites in a high-gas regime: at 15 gwei the same round trip costs about $22, which is 22 basis points on $10,000 and 220 basis points on $1,000. Check the live gas price before assuming either.
​

For sub-$10K stablecoin deposits, the decision used to be which chain charges the lowest gas. With mainnet base fees at fractions of a gwei, that edge has largely collapsed and L2 deployments (Aave V3 on Base, Morpho on Base, Spark on Base) win on convenience rather than on cost. Coinbase USDC rewards carry no gas at all because the position is custodied, but the Coinbase One membership required to earn them is itself a fixed cost of $59.88 a year, which is 0.6% on a $10,000 balance and 6% on a $1,000 balance. Fixed costs did not disappear; they moved from the chain to the subscription. Compare the live figures at DeFiLlama and Etherscan's gas tracker before choosing.
​

Most jurisdictions treat stablecoin yield as ordinary income at the moment it accrues to the depositor, not when withdrawn. In the United States, the IRS has not issued definitive guidance on every yield product, but the standard interpretation (per IRS Notice 2014-21 and subsequent guidance) is that crypto income is taxable in the year received at fair market value. A 5% USDC yield held by a US taxpayer in the 32% federal bracket nets to 3.4% after federal tax, before state tax.
​

Two structural differences matter for tax. Yield-bearing wrappers (sUSDS, sUSDe, sDAI) that change balance internally rather than transferring tokens may delay the taxable event until the wrapper is unwound, depending on jurisdiction and accounting method. Per-block rebasing (aTokens on Aave) is more clearly continuous income. The tax treatment of token-emissions yield is also distinct from real yield: emissions tokens are typically taxed as income at receipt and again as capital gains/losses on sale. This is jurisdiction-specific and changes; the figures in this article are pre-tax. Always confirm with a crypto-aware accountant.
​

The matrix below shows what a $10,000 USDC deposit held for one year returns across four common venues, with every rate pulled on September 16 2026 from DeFiLlama and Coinbase's USDC page. Quoted APY is the venue headline. Net APY adjusts for fees and for gas at that day's mainnet base fee. Dollar figures are pre-tax, and variable rates move.
​

The ranking is now set by the headline rate and the subscription, not by gas. Morpho's Steakhouse USDC vault leads at 4.57%. Aave V3 on mainnet and Sky's sUSDS sit within three basis points of each other. Coinbase finishes last on a $10,000 balance, because the membership fee that gates the 3.50% rate costs 60 basis points at that size, which is exactly the drag mainnet gas used to impose. Rates per DeFiLlama and Coinbase's USDC page on that date.
​

For deposits 5x larger ($50K), the ordering barely moves: gas is already immaterial, and the Coinbase membership drops to 12 basis points, lifting its net to 3.38%. At $1,000 the picture inverts for Coinbase alone: $59.88 of membership against $35 of gross rewards is a net loss, while the onchain venues keep almost their full headline rate. Headline rates per DeFiLlama.
​

Eco Routes settles USDC across 15+ supported chains, including Base, Arbitrum, Optimism, Polygon, Celo, and Ethereum mainnet. For depositors comparing yield platforms across chains (Morpho on Base versus Aave on Ethereum, for example), Eco intents handle the bridge and the destination-chain gas in a single transaction, eliminating the need to hold native gas tokens on the destination. Eco is one of several USDC routing options; Circle's CCTP, Across, and LI.FI are also live. None of these change the underlying protocol APY; they affect entry/exit gas drag, which is the dominant variable on small deposits.
​

APR is the annualized rate without compounding. APY is APR after compounding is applied. At an APR of 5% compounded continuously, APY is 5.127%, which is arithmetic rather than a quoted rate. Most onchain lending front-ends (Aave, Morpho, Spark) display APY directly. Liquidity-mining dashboards often display APR for reward tokens; convert to APY before comparing.
​

It generally does not, at the gas prices prevailing in September 2026. Coinbase rewards carry no gas because the position is custodied, but the Coinbase One membership that gates them costs $59.88 a year, while a mainnet round trip on Aave costs about $0.11 at a 0.078 gwei base fee per Etherscan's gas tracker. The fixed cost now sits on the custodial side, so for sub-$10K accounts Aave mainnet usually nets higher than Coinbase.
​

Yes. Emissions yield (CRV, AAVE, MORPHO, BAL, etc.) requires selling the token to realize value, exposing the depositor to token price drift. No published figure fixes the right discount, so choose one and apply it consistently across every pool you compare. Real yield paid in the deposit asset (USDC interest on Aave, SSR on Sky) does not require this conversion.
​

Most jurisdictions treat stablecoin yield as ordinary income at receipt. In the United States, the IRS has indicated crypto income is taxable in the year received at fair market value. Yield-bearing wrappers like sUSDS may delay the taxable event until unwound, depending on accounting method. Consult a crypto-aware accountant; this article is not tax advice.
​

At the mainnet base fees prevailing in September 2026, gas no longer decides it. On September 16 2026, Aave V3 quoted 3.57% on Ethereum and 3.64% on Base, and the Morpho Steakhouse USDC vault quoted 4.57%, per DeFiLlama. Coinbase's 3.50% is the wrong answer at this size, because the $59.88 annual membership needed to earn it exceeds the rewards a $1,000 balance would generate.
​

Sources and methodology. APY and APR rates pulled from DeFiLlama yields on September 16, 2026. Aave V3 reserve factor and per-block accrual from Aave documentation. Morpho Blue vault fees from Morpho documentation. Sky Savings Rate from Sky governance documentation. Coinbase USDC rewards rate and Coinbase One membership pricing from Coinbase USDC page. Pendle PT mechanics from Pendle documentation. Gas drag is computed from the 0.078 gwei base fee and per-action costs published by Etherscan's gas tracker on September 16, 2026. Tax framing references IRS Notice 2014-21; not tax advice. Figures refresh quarterly; APYs are variable and may have moved since publication.
​