What does a loan cost on Ethereum mainnet?

TL;DR. A loan on Ethereum mainnet has three costs: gas for each transaction, the protocol's fee, and interest. We measured the gas for every step of a crowd loan on Unlloo. At the gas price on 28 October 2026 (0.208 gwei, ETH at $2,333), a borrower pays about $0.36 in gas for a whole loan (approve, request, accept, repay) and a lender about $0.22 (approve, offer, claim). At 2 gwei those become $3.44 and $2.08; at 20 gwei, $34 and $21. Mainnet gas has spent most of 2026 below 1 gwei. The fee is 10% of the interest and nothing of the principal, fixed for each loan when it is created. Interest is simple, accrues per second at the rate each lender offered, and on a 1,000 USDC loan at 8% for 90 days comes to 19.73 USDC, of which the lenders keep 17.75.

What are the three costs of a loan on Ethereum?

Every loan on Ethereum costs gas, a fee and interest, and they are paid to three different parties. Gas is paid to the network for each transaction you send; it is the only cost that has nothing to do with the loan's size. The protocol fee is paid to the lending protocol for running the contract. Interest is paid by the borrower to whoever lent the money, and on a pooled protocol a slice of it also goes to the protocol as its fee. How DeFi interest rates are set covers the rate itself; this post adds up all three for one concrete case, a crowd loan on Unlloo, where lenders choose the borrower and name a rate and nothing is locked as collateral.

The reason to add them up is that the first cost is the one people get wrong. The idea that Ethereum mainnet is too expensive for a small loan dates from 2021, when gas ran at tens of gwei. The numbers below are for 2026.

How is a gas fee calculated?

A gas fee is the gas a transaction uses multiplied by the price per unit of gas, and that price is quoted in gwei, a billionth of an ETH. The gas used depends only on what the transaction does: a plain ETH transfer uses 21,000 gas, a token transfer around 40,000 to 65,000, and a loan contract call a few hundred thousand, because it writes more to the chain's storage. The price per unit is set by the network, not by the protocol: since the 2021 fee reform (EIP-1559) each block has a base fee that rises when blocks are more than half full and falls when they are less, plus a small priority fee you add to be included faster.

In 2026 that base fee has been low for most of the year. Ethereum's own guide to building on Ethereum in 2026 puts it this way: the block gas limit was raised from 30 million to 60 million during 2025, rollups now carry about 95% of transactions, mainnet usually runs below its block target, and daily average gas ran near 0.5 gwei through April 2026. It calls the old assumption of a 10 to 30 gwei mainnet stale. On 11 October 2026 the base fee averaged 0.0673 gwei over 24 hours, with blocks running half empty for days, according to CryptoTicker; YCharts lists a daily average of 0.54 gwei on 5 August 2026, down 74% on a year earlier. It is not always that low: Etherscan's tracker showed 1.9 gwei on 7 October and 0.061 gwei on 27 October. The snapshot we use for the dollar figures below is Etherscan's gas tracker on 28 October 2026 at 14:02 UTC: 0.208 gwei, with ETH at $2,333.

The arithmetic is short. Cost in dollars = gas used × gas price in gwei × ETH price ÷ 1,000,000,000. A 200,000-gas transaction at 0.208 gwei and $2,333 is 200,000 × 0.208 × 2,333 ÷ 10⁹ = $0.097. At 2 gwei it is $0.97, and at 20 gwei $9.71. Every figure that follows scales the same way, so if gas is ten times higher on the day you read this, multiply by ten.

How much gas does each step of a crowd loan use?

A crowd loan on Unlloo takes between five and seven transactions from request to the last lender's claim, and we measured each one. The ranges come from running the deployed contract code under Hardhat's gas reporter through full loan lifecycles; the single values are from the contract's own transactions on mainnet, which anyone can read on its Etherscan page. Approving the token is a transaction on the stablecoin's contract, not ours; USDC's approve used about 55,600 gas in the approvals that preceded the first mainnet offers, and ethereum.org's guide gives about 46,000 as a typical figure for a token approve.

Three things in the table are worth knowing. Submitting an offer costs more than creating the request because it also moves the lender's stablecoins into the contract, where they stay in escrow until the borrower accepts or the lender withdraws. Accepting costs about 60,000 gas more for each additional offer accepted, because each one is written to the loan. And the first transaction of any kind on a fresh storage slot costs more than later ones, which is why the mainnet figures sit at the top of the ranges: those were the first loans and the first offer the contract had ever recorded.

What does a whole loan cost in gas, for each side?

For the borrower, a whole loan is four transactions: approve the token for repayment, create the request, accept the offers and repay. With one accepted offer and one repayment that is about 738,000 gas, which is $0.36 at 0.208 gwei, $3.44 at 2 gwei and $34 at 20 gwei. For a lender it is three: approve, offer and claim, about 446,000 gas, which is $0.22, $2.08 and $21 at the same three prices. A borrower who accepts three offers and repays in two instalments adds roughly 120,000 gas for the extra offers and 240,000 for the second repayment, which at 0.208 gwei is another $0.17.

The first offer on mainnet is a real example. It was submitted on 27 October 2026 for 99 USDC at 4.2%, used 261,952 gas at 0.653 gwei, and cost the lender 0.000171 ETH, about $0.40 at the time, which is 0.4% of the amount offered. The two loan requests that preceded it, for 200 and 500 USDC, cost their borrowers about $0.10 and $0.50 to create, the second one at a gas price four times the first.

What does the protocol fee cost?

The protocol fee on Unlloo is 10% of the interest and nothing of the principal, and the rate is fixed for each loan when it is created. The contract takes it out of each interest payment as it is repaid, before the lenders' share, so a lender who offers at 8% receives 7.2% net; the app shows offers and projected returns net of the fee so there is no second calculation to do. The fee can be changed only by queueing a new rate behind a 3-day timelock, the contract caps it at 25% whatever is queued, and a change applies only to loans created after it takes effect; a loan that started at 10% keeps 10% until it closes, as the security page sets out.

In money, on a 1,000 USDC loan at 8% for 90 days the interest is 19.73 USDC, the fee is 1.97 and the lenders keep 17.75. On a 200 USDC loan at 5% for 30 days the interest is 0.82 USDC and the fee is 8 cents. Because the fee is a share of interest, a loan that is never repaid pays no fee: the protocol earns only when the lenders do.

How is interest calculated, and what does it cost?

Interest on a crowd loan is simple interest, accrued every second on the principal still outstanding, at the rate each lender offered, with a year counted as 365 days. There is no compounding: interest does not earn interest. When several lenders at different rates fund one loan, the contract weights each lender's rate by the amount it accepted from them, so a borrower who takes 400 USDC at 7%, 400 at 8% and 200 at 9% pays a blended 7.8%. The borrower sets a maximum rate on the request and lenders offer at or below it, which is how the rate is found; the rate can never exceed 50%, a ceiling written into the contract.

Repaying early costs less, not more: a partial repayment reduces the principal that interest accrues on from that second, and there is no early-repayment charge. Repaying late costs more in the plainest way: if the deadline passes with a balance outstanding, the loan is marked as not repaid in time, interest keeps accruing at the same rate on what is left, and a full repayment after that closes the loan as repaid late. There is no separate penalty rate in the contract; the penalty is the record, which what happens if you don't repay covers.

Is a 200 USDC loan worth it on mainnet?

At 2026 gas prices, yes: the borrower's gas for a whole 200 USDC loan is $0.36, or 0.18% of the principal, at 0.208 gwei. The question only turns on the days gas spikes. The table puts the borrower's whole-loan gas against the principal at the three prices, next to the interest a 30-day loan at 8% would cost.

Read the first row across. At 0.208 gwei the gas on a 200 USDC loan is a quarter of one month's interest; at 2 gwei it is two and a half times the interest, and the loan is still cheaper than most alternatives for someone without collateral; at 20 gwei it is a sixth of the principal and worth waiting out. For a lender the same logic applies to the size of an offer: a 50 USDC offer at 0.208 gwei costs $0.22 to place and claim, which is 0.44% of the offer and more than the interest a month at 5% would earn on it, so small offers want a cheap gas day or a longer term.

How do you pay less gas?

You pay less gas by sending transactions when gas is cheap, which the loan's timing allows, and by sending fewer of them.

• Use the windows. A funding window is at least an hour and usually days, the borrower has up to seven days after it closes to accept, and repayment is due by a date the borrower chose. None of these steps has to be sent in the hour you first look at it. Check the gas tracker and send on a quiet hour; weekends and early mornings in Europe and America are usually cheapest. The one step not to leave for a cheap hour is repayment near its deadline.
• Accept the offers you need, not all of them. Each accepted offer adds about 60,000 gas to the accept transaction and a claim transaction for that lender later. A borrower who can cover the request with two offers instead of five saves gas on both sides.
• Repay once, claim once. Each repayment is a transaction, and a lender who claims after each partial repayment pays for each claim. Repaying in full in one transaction, then claiming once, is the cheapest path. In the app, "Full amount" adds ten minutes of interest at the loan's maximum rate so that the repayment still closes the loan if it takes a few minutes to be mined.
• Approve once per token. The approval is on the stablecoin's contract and is needed before your first offer or repayment in that token. Approving exactly the amount you are about to use is the safer habit, and it costs the same gas as approving more.

What does not help: there is no cheaper network to use for the same loan, because Unlloo runs on Ethereum mainnet with USDC, USDT and DAI only. The trade-off is deliberate. A rollup would cut gas further, but the borrowers' wallet histories, the stablecoin issuers' main contracts and the deepest liquidity are on mainnet, and at 2026 prices the gas is already a rounding error on any loan above a few hundred dollars.

Who pays when a loan is cancelled or expires?

Whoever sends the transaction pays its gas, and the exits are the cheapest transactions in the contract. A borrower who cancels an unfunded request pays about 39,000 gas, $0.02 at 0.208 gwei. A lender whose offer was not accepted, or whose request was cancelled or expired, withdraws their funds for 64,000 to 81,000 gas, $0.03 to $0.04. Marking an unfunded request expired, so that its status is right for everyone, costs about 41,000 gas and can be sent by anyone. If the contract is ever paused, these exits still work: pausing blocks only new requests, new offers and acceptances, never repayment, claims or withdrawals.

So the full picture, for a 1,000 USDC loan at 8% over 90 days on a normal 2026 day: the borrower pays about 36 cents in gas and 19.73 USDC in interest; the lenders receive 17.75 USDC and pay about 22 cents each in gas; the protocol takes 1.97 USDC. The part that is new in a crowd loan is not the cost. It is that the 17.75 goes to people who chose this borrower, at a rate they named.

Sources

1. ethereum.org, "Building on Ethereum in 2026: what has changed", read on 28 October 2026. The gas limit raised from 30 million to 60 million, rollups carrying about 95% of transactions, daily averages near 0.5 gwei through April 2026, and the example costs of an ETH transfer, a token transfer and a token approve.
2. Etherscan, "Gas Tracker", snapshots of 7, 27 and 28 October 2026. The 0.208 gwei base fee and $2,333 ETH price used for every dollar figure.
3. CryptoTicker, "Ethereum base fee at 0.0673 gwei, a sixth of the week", 11 October 2026. The 24-hour and 7-day base fee averages and the half-empty blocks behind them.
4. YCharts, "Ethereum Average Gas Price (Daily)", read on 28 October 2026. The 0.5361 gwei daily average on 5 August 2026 and the fall of 74% over a year.
5. Unlloo's CrowdLoanManager contract on Etherscan, read on 28 October 2026. The gas used by the first two loan requests and the first offer on mainnet, and the USDC approvals that preceded them.
6. Hardhat gas reporter over the deployed contract code, run on 28 October 2026 through full loan lifecycles with one and three lenders, partial and full repayment, cancellation and expiry. The gas ranges in the first table.
7. Unlloo, "Security". The 10% fee on interest, the 25% cap, the 3-day timelock, the per-loan fee snapshot, the 50% rate ceiling and what pausing blocks.