Here is a trap built into the vocabulary: lenders and comparison sites use the phrase “simple interest loan” for two different structures that price the same loan hundreds or thousands of dollars apart — and most comparison pages never notice they are mixing them. In one structure, interest is precomputed on the original amount for the whole term and locked in at signing. In the other, interest is charged only on the balance you still owe, but you repay principal in equal slices, so payments shrink over time. Both get called “simple interest.” This page separates the two, then prices both against a standard amortizing loan on one identical example, so you can see what each label is really worth.
General information, not financial advice. All figures in the worked example are computed from the stated inputs; the structure in your note governs your loan. How each interest method accrues, step by step, is covered in how business loan interest is calculated.
Precomputed (flat) interest. Interest is calculated once, up front, on the original principal for the entire term, then added to the principal and divided into equal payments. The interest does not shrink as your balance falls — it was fixed on day one. This is the sense Fundera and most short-term-loan coverage use, and it is typical of short-term online loans. Its defining feature: paying early saves you none of the interest, because the interest was never being charged on your remaining balance in the first place.
Equal-principal (non-blended) interest. Interest is charged on the declining balance — the honest, “simple” way — but instead of blending principal and interest into a level payment, you repay the same amount of principal every month, plus whatever interest the current balance generates. Payments start high and fall every month. This is the structure in BDC’s glossary treatment of non-blended loans, and it is common in some bank and development-lender products.
Amortizing (blended). The standard bank term loan: interest on the declining balance, principal portions that grow over time, one level payment throughout. Extra payments reduce the balance and therefore reduce future interest — the baseline the other two should be judged against.
Same loan throughout: $30,000, 18 months, a 12% headline rate.
| Structure | Monthly payment | Total interest | Total repaid |
|---|---|---|---|
| Precomputed simple interest | $1,966.67, flat | $5,400.00 | $35,400.00 |
| Amortizing at 12% APR | $1,829.46, flat | $2,930.31 | $32,930.31 |
| Equal-principal (non-blended) | $1,966.67 falling to $1,683.33 | $2,850.00 | $32,850.00 |
The arithmetic, briefly. Precomputed: $30,000 × 12% × 1.5 years = $5,400 of interest, set before you make a single payment; ($30,000 + $5,400) ÷ 18 = $1,966.67. Amortizing: the standard payment formula on the declining balance gives $1,829.46 a month and $2,930.31 of interest in total. Equal-principal: $30,000 ÷ 18 = $1,666.67 of principal monthly, plus 1% of whatever balance remains — $300 of interest in month one, $16.67 in the last — totalling $2,850.00.
Two things stand out. First, the precomputed loan costs $2,470 more than the amortizing loan at the same headline rate — the rate was never the difference; the structure was. Second, a coincidence worth remembering: the precomputed loan’s flat payment ($1,966.67) is identical to the equal-principal loan’s first payment. Same number, entirely different loans underneath — in one it never falls, in the other it drops every month while interest melts away.
This is where the structures stop being academic. On an amortizing loan, every extra dollar of principal removes that dollar from all future interest calculations — pay $5,000 extra and you save interest on $5,000 for every remaining month (run the effect in the amortization calculator; just check your note for a prepayment penalty first). On an equal-principal loan, early payment saves interest the same way, because interest rides on the balance. On a precomputed loan, early payoff saves $0 of interest: the $5,400 was baked into the amount you owe the day you signed. Fundera makes the same point in its comparison — it is the single most important difference between the labels, and it never appears in the headline rate.
Where each structure shows up in the market (attributed): short-term online loans skew precomputed or factor-priced, while bank term loans amortize. Factor pricing — a multiplier like 1.25× the amount borrowed rather than a rate at all — is the third sibling; it behaves like precomputed interest in that the cost is fixed at funding, and our working capital calculator prices it side by side with APR so the difference is visible. Whenever a quote arrives as a flat fee, a factor, or “simple interest” with no amortization schedule attached, ask for the schedule. If there isn’t one, you are almost certainly looking at the precomputed kind.
What is the difference between an amortizing loan and a simple interest loan? An amortizing loan charges interest on your declining balance and blends principal and interest into one level payment, so extra payments save you interest. “Simple interest” can mean two things: a precomputed loan, where interest is calculated once on the original amount for the whole term and paying early saves nothing, or an equal-principal loan, where interest is charged on the declining balance but principal is repaid in equal slices and payments fall over time (Crestmont’s and BDC’s treatments use the term differently). On $30,000 over 18 months at 12%, the three structures cost $5,400, $2,930 and $2,850 in interest respectively.
Do I save money by paying off a simple interest loan early? Only if your “simple interest” loan charges interest on the declining balance (the equal-principal kind). If it is precomputed — interest fixed on the original principal for the full term at signing — paying early saves you no interest at all, as Fundera’s comparison stresses. Check the note: if the total interest was stated as a fixed dollar amount at origination, it is precomputed.
Which is better, simple interest or amortized? On identical amount, rate and term, an amortizing loan is cheaper than a precomputed “simple interest” loan and rewards early payment — $2,930 versus $5,400 of interest on the example above (themoneyknowhow’s comparison framing reaches the same ordering). Equal-principal loans are cheapest of all on total interest but demand their highest payments up front. The real answer is to compare total interest and the early-payoff treatment, not the label.
General information, not financial advice. Sources: Fundera “Amortization vs. Simple Interest Loans”; BDC glossary (non-blended loans); Crestmont simple-interest explainer; themoneyknowhow comparison. Worked example computed from the stated inputs. Currency verified 2026-10-23.