Small Business Loan Calculator and Payment Guide

How to Calculate Monthly Loan Payments

Standard business term loans use amortizing payments, meaning each monthly payment includes both principal repayment and interest. The payment amount stays the same each month, but the split between principal and interest shifts over time. Early payments are mostly interest. Later payments are mostly principal.

The formula for calculating a fixed monthly payment is: Payment = Principal x (Rate / 12) / (1 - (1 + Rate / 12) ^ (-Months)). Rate is the annual interest rate as a decimal (10% = 0.10), and Months is the total number of monthly payments.

You do not need to memorize this formula. Any spreadsheet (Google Sheets, Excel) has a PMT function that calculates it for you. In Google Sheets, the formula is: =PMT(annual_rate/12, number_of_months, -loan_amount). For a $50,000 loan at 10% APR over 5 years (60 months): =PMT(0.10/12, 60, -50000) returns $1,062.35 per month.

Payment Examples at Common Loan Amounts

Here are monthly payments and total interest for common loan scenarios. All examples use standard amortizing repayment.

$25,000 loan: At 8% APR for 3 years, monthly payment is $783, total interest is $3,199. At 12% APR for 3 years, monthly payment is $830, total interest is $4,899. At 20% APR for 3 years, monthly payment is $929, total interest is $8,432. At 30% APR for 2 years, monthly payment is $1,346, total interest is $7,296.

$50,000 loan: At 8% APR for 5 years, monthly payment is $1,014, total interest is $10,831. At 11% APR for 5 years, monthly payment is $1,087, total interest is $15,228. At 15% APR for 3 years, monthly payment is $1,733, total interest is $12,388. At 25% APR for 2 years, monthly payment is $2,649, total interest is $13,580.

$100,000 loan: At 10% APR for 7 years, monthly payment is $1,661, total interest is $39,496. At 11% APR for 5 years, monthly payment is $2,174, total interest is $30,456. At 15% APR for 3 years, monthly payment is $3,467, total interest is $24,806. At 20% APR for 2 years, monthly payment is $5,090, total interest is $22,168.

$200,000 loan: At 10% APR for 10 years, monthly payment is $2,644, total interest is $117,240. At 11% APR for 7 years, monthly payment is $3,476, total interest is $91,984. At 13% APR for 5 years, monthly payment is $4,567, total interest is $74,008.

The pattern is clear: lower rates and longer terms dramatically reduce monthly payments but increase total interest paid. A $100,000 loan at 10% over 7 years costs $39,496 in total interest but requires only $1,661 per month. The same loan at 15% over 3 years costs $24,806 in total interest (less) but requires $3,467 per month (more than double). Choose based on what your cash flow can support while keeping the total cost reasonable.

Calculating Factor Rate Costs

Factor rate loans (common with merchant cash advances and some online lenders) are simpler to calculate but more expensive than they appear. Total repayment equals the advance amount multiplied by the factor rate. A $40,000 advance at a 1.3 factor rate means you repay $52,000 total ($40,000 x 1.3). The cost is $12,000.

To convert a factor rate to an approximate APR, use this formula: APR = (Factor Rate - 1) / (Repayment Period in Years x 0.5). The 0.5 accounts for the declining average balance over the repayment period. For a 1.3 factor rate repaid over 6 months (0.5 years): APR = (1.3 - 1) / (0.5 x 0.5) = 0.30 / 0.25 = 1.20, or approximately 120% APR. For the same factor rate repaid over 12 months: APR = 0.30 / (1.0 x 0.5) = 0.60, or approximately 60% APR.

This formula provides an approximation. The exact APR depends on the specific payment schedule (daily vs weekly vs monthly) and whether payments are fixed or revenue-based. But the approximation is close enough for comparison purposes and consistently reveals that factor rates translate to much higher APRs than most borrowers realize.

Calculating Revenue-Based Financing Costs

Revenue-based financing uses a flat fee on the advance amount. A $60,000 advance with a 10% fee means you repay $66,000 total. The $6,000 cost is fixed regardless of how long repayment takes. The effective APR depends entirely on repayment speed.

If your daily revenue average results in repayment over 4 months: APR is approximately 30% to 35%. Over 6 months: approximately 20% to 24%. Over 9 months: approximately 13% to 16%. Over 12 months: approximately 10% to 12%. The longer repayment stretches, the lower the effective APR, because you had access to the capital for a longer period for the same flat cost.

This is the opposite of traditional loans, where faster repayment reduces total cost. With revenue-based financing, faster repayment does not save you money (the fee is fixed), it just means you paid the same fee for shorter access to capital. Understanding this dynamic is critical when comparing revenue-based offers to traditional loans.

The Break-Even Calculation: Does This Loan Make Sense?

Before accepting any financing, calculate whether the investment funded by the loan generates returns that exceed the total borrowing cost. This is the fundamental question that determines whether borrowing is a good or bad decision.

The formula is straightforward: (Expected Revenue from Investment - Cost of Investment - Loan Interest Cost) = Net Profit or Loss. If the result is positive, the loan creates value. If negative, the loan destroys value.

Example: you want to borrow $30,000 to purchase inventory that you project will generate $75,000 in revenue over 6 months. Your cost of goods is the $30,000 in inventory. Your gross revenue is $75,000. Your gross profit before financing is $45,000. If the loan costs $3,000 in interest (10% APR for 6 months), your profit after financing is $42,000. The loan clearly makes financial sense because the return ($42,000) far exceeds the cost ($3,000).

Different example: you want to borrow $20,000 to redesign your website, hoping to increase conversions. You estimate the redesign might increase revenue by 15%, but you are not sure. Your current monthly revenue is $15,000, so a 15% increase would add $2,250 per month, or $27,000 per year. If the loan costs $4,000 in interest over 2 years, your net gain would be $23,000 if the 15% estimate is accurate. But if the actual increase is only 5% ($9,000 per year, $18,000 over 2 years), your net gain drops to $14,000. Still positive, but the uncertainty makes this a riskier investment of borrowed capital.

As a general rule, use borrowed capital for investments with predictable, near-term returns (inventory purchases, proven marketing channels, equipment that directly reduces costs). Avoid borrowing for investments with uncertain or long-term returns (rebranding, speculative product launches, general "growth") unless you can absorb the loan payments from existing cash flow if the investment underperforms.

Total Cost of Borrowing Comparison

Here is the total cost of borrowing $50,000 across different financing types, assuming similar repayment timelines where applicable. SBA 7(a) loan at 11% APR for 5 years: $15,228 total interest, $1,087 monthly payment. Bank line of credit at 10% APR, drawn for 12 months: $5,000 total interest. Online term loan at 25% APR for 2 years: $13,580 total interest, $2,649 monthly payment. Revenue-based financing at 10% flat fee: $5,000 total cost, repaid in 6 to 12 months. Shopify Capital at 14% flat fee: $7,000 total cost, repaid in 6 to 12 months. Merchant cash advance at 1.3 factor rate: $15,000 total cost, repaid in 4 to 8 months.

The cheapest total cost for long-term capital (12+ months) is SBA or bank financing. The cheapest for short-term capital (under 12 months) is a bank line of credit or revenue-based financing. The most expensive regardless of timeline is merchant cash advances. When evaluating any financing offer, calculate the total dollar cost and compare it to this benchmark table to see where the offer falls.