Peer-to-Peer Lending ROI Calculator
Introduction
Peer-to-peer lending can look simple on the surface: you contribute money, borrowers pay interest, and your account balance grows over time. In practice, the return you actually earn depends on several moving parts. The headline interest rate matters, but so do defaults, the consistency of your monthly contributions, how long you stay invested, and whether your cash remains fully deployed. This calculator is designed to give you a practical estimate of portfolio growth under a clear set of assumptions, not to promise a guaranteed outcome.
The tool works best when you use it for planning rather than prediction. You enter a monthly deposit amount, an annual interest rate, a term in months, and an expected default rate. The calculator then estimates a future value for your contributions after applying compound growth and a simple default haircut. That makes it useful for comparing scenarios such as cautious, baseline, and optimistic cases. If you are deciding how much to allocate to P2P lending, this kind of side-by-side modeling is usually more helpful than relying on a single advertised yield figure.
It is also important to understand what this calculator does not do. It does not model note-by-note cash flows, servicing fees, taxes, recovery timing, or periods when repayments sit idle before being reinvested. Those details can matter in real portfolios. Even so, a simplified model is still valuable because it helps you think clearly about the main drivers of return. By making your assumptions explicit, you can test whether a strategy still looks reasonable after accounting for losses instead of focusing only on gross interest.
If you already invest through a lending platform, this page can help you review whether your expectations still match reality. If you are new to the space, it can help you understand how recurring deposits and compounding interact with credit risk. In both cases, the most responsible way to use the calculator is to revisit your assumptions regularly and compare them with actual platform performance.
How This Peer-to-Peer Lending ROI Estimate Works
Peer-to-peer lending projections often appear attractive because the quoted rates can be much higher than what you might see in savings products or short-term cash accounts. The tradeoff is that P2P returns are not driven by interest alone. Borrower defaults, platform fees, reinvestment delays, and portfolio concentration all affect what you keep. This calculator gives you a structured way to estimate growth by combining recurring deposits with a stated rate assumption and then reducing the result by an expected default percentage.
That approach is intentionally simple. It does not attempt to reproduce every cash flow from every loan. Instead, it answers a practical planning question: if you contribute a fixed amount each month and earn an average return over a set period, what might your account be worth after allowing for losses? For many investors, that is the right starting point. It helps you compare strategies, test whether your assumptions are realistic, and decide whether the expected reward is worth the risk.
What Each Input Means
The monthly deposit is the amount of new money you plan to add on a regular basis. If you contribute $200 every month, the calculator assumes you keep doing that for the full term you enter. The annual interest rate is your expected yearly return before the default adjustment in this model unless you intentionally enter a net rate that already reflects losses and fees. The loan term in months is the total length of time over which deposits and growth are modeled. The expected default rate is a simplified estimate of how much of the portfolio may be lost to nonpayment over the modeled period.
Consistency matters when choosing these inputs. If your platform reports a net annualized return after fees and losses, you may decide to enter that lower net rate and use a default rate of zero for a quick estimate. If you want more transparency, you can enter a gross rate and then apply a separate default assumption. Both methods can be useful, but you should avoid mixing them in a way that counts the same risk twice.
For example, suppose a platform advertises a 10% gross yield, but your historical experience after defaults and fees is closer to 7.5%. You could either enter 10% and a default assumption that roughly captures the drag, or enter 7.5% and set defaults to zero for a net-return scenario. What you should not do is enter 7.5% and then also apply a large default haircut unless you are deliberately stress testing a worse outcome.
Formula
The calculator uses the future value of an ordinary annuity and then applies a default reduction. In plain language, each monthly deposit has less time to compound than the deposits made before it, so the formula adds up the growth of a stream of equal monthly contributions. After that, the model reduces the total by the expected default rate.
Formula: F = M (1+r^n - 1) / r × (1 - d)
In this expression, is the monthly deposit, is the monthly interest rate, is the number of months, and is the default rate expressed as a decimal. The script converts the annual percentage rate into a monthly rate by dividing by 12 and by 100. If the interest rate is zero, the calculator falls back to a simpler case: total deposits multiplied by one minus the default rate.
This is a useful approximation, but it is still an approximation. In real lending portfolios, defaults do not happen all at once, recoveries may arrive later, and repayments may be reinvested at changing rates. The formula is best understood as a planning model that summarizes those effects into a manageable set of assumptions.
Example
Imagine you plan to invest $100 per month for 36 months and expect an annual return of 7%, with a 3% default rate over the period. Your total contributions would be $3,600. Because each monthly deposit has time to earn interest, the estimated future value would be higher than your contributions alone, but the default assumption would reduce the final amount somewhat. When you enter those numbers into the calculator, the result gives you a quick estimate of what the portfolio might be worth under those conditions.
This kind of example shows why compounding and credit losses need to be considered together. A moderate interest rate can still produce meaningful growth when contributions are regular and reinvestment is steady. At the same time, even a small default assumption can noticeably reduce the ending value, especially over longer periods or in portfolios with thin diversification. That is why many investors run several versions of the same example with different default rates before making allocation decisions.
Interpreting the Result
The result area shows three ideas that should be read together. First, the estimated future value is the projected ending balance after growth and the default adjustment. Second, total contributions show how much money you personally added over the full term. Third, net growth after defaults compares the projected ending value with the amount you contributed. If net growth is positive, the model suggests your return more than offset the assumed losses. If it is negative, the combination of rate, term, and defaults was not enough to produce a gain over your contributions.
A positive result does not automatically mean the investment is attractive. You still need to compare it with alternatives such as bonds, high-yield savings, certificates of deposit, or diversified stock and bond funds. You should also consider liquidity. Many P2P loans cannot be sold quickly without a discount, and some platforms offer limited or no secondary market support. A return estimate only becomes meaningful when viewed alongside risk, taxes, and access to cash.
Scenario Planning and Risk Awareness
One of the best uses of this calculator is scenario planning. Instead of entering a single optimistic rate and moving on, try a conservative case, a baseline case, and an optimistic case. In a conservative case, you might lower the interest rate and raise the default rate to reflect weaker underwriting conditions or a recession. In a baseline case, you can use assumptions that match recent platform experience. In an optimistic case, you can test what happens if defaults stay low and reinvestment remains efficient. If your plan only works in the optimistic case, that is a warning sign.
Diversification is especially important in peer-to-peer lending because a small number of defaults can have an outsized effect when your portfolio is concentrated. If you spread your money across many borrowers, grades, and origination periods, the impact of any one loan failure is smaller. This calculator does not model note-level concentration directly, so your default assumption should reflect how diversified your actual strategy is. A concentrated portfolio deserves a more conservative default input than a broad one.
Cash drag is another factor worth remembering. In real accounts, repayments may sit uninvested for days or weeks before they are redeployed. That lowers realized returns compared with a model that assumes smooth compounding. If your platform often leaves cash idle, consider reducing the rate input slightly to make your estimate more realistic. The same idea applies to servicing fees and taxes. If those costs are meaningful, adjust your assumptions rather than treating the calculator output as a final net result.
Limitations
This calculator uses a simplified compound-growth framework. It assumes a constant monthly contribution, a stable average interest rate, and a single default adjustment applied to the modeled value. Real portfolios are messier. Borrowers may prepay early, defaults may cluster in certain credit bands, recoveries may arrive late or not at all, and platform policies can change over time. The model also does not include taxes, servicing fees, inflation, or differences in loan seasoning.
Because of those limitations, the output should be treated as an estimate for education and planning, not as financial advice or a guaranteed forecast. It is most useful when paired with judgment, diversification, and periodic review of actual results. If your realized performance differs from the estimate, that does not necessarily mean the calculator failed; it may mean your assumptions need to be updated. In that sense, the tool is most valuable as part of an ongoing decision process rather than a one-time answer.
Past platform performance is not a promise of future returns. Credit conditions, borrower quality, regulation, and platform operations can all change. Use the calculator to ask better questions, compare alternatives, and stress test your expectations before committing capital.