Interest on a business line of credit accrues only on the amount you borrow — not your full credit limit — and is typically calculated using a daily balance method based on your annual percentage rate (APR).

Understanding how that interest compounds, what fees get folded into your total cost, and how variable rates can shift your payments over time is what separates a good financing decision from a costly one.

What is interest on a business line of credit?

Interest on a business line of credit is the cost you pay to borrow money from your available credit, and it only applies to what you’ve actually drawn, not your total limit.

Your lender sets a maximum credit limit — say, $50,000 — and you can borrow from it, repay it, and borrow again as needed. As you draw funds, interest begins accruing on the outstanding balance. Once you repay, that interest stops.

So if you have a $50,000 line and draw $10,000, you’re only paying interest on that $10,000. The remaining $40,000 sits available at no cost (at least where interest charges are concerned.) This is what separates a line of credit from a term loan, where interest accrues on the full lump sum from day one, regardless of how much you actually use.

Interest rate vs. APR: What’s the difference?

This is the distinction that trips up most business owners — and it matters a lot when comparing lender offers.

The interest rate (sometimes called the “nominal rate”) is the base cost to borrow, expressed as an annual percentage. It doesn’t include fees. 

APR is the interest rate plus certain fees, expressed as a single annual figure. Because APR folds in costs like origination fees and annual maintenance fees, it’s almost always higher than the base interest rate.

APR is also the most reliable metric for comparing two different lender offers side by side. 

Two lenders might both advertise a 9% interest rate. But if one charges a 2% origination fee and a $150 annual fee, and the other charges nothing beyond interest, the APRs will be meaningfully different — and so will your actual cost of borrowing.

Always ask for the APR, not just the interest rate, when evaluating a line of credit.

How interest is calculated on a business line of credit.

Most lenders calculate interest using the average daily balance method. Here’s how it works:

  1. Your lender divides your APR by 365 to get a daily periodic rate. At a 12% APR, that’s roughly 0.0329% per day.
  2. That daily rate is multiplied by your outstanding balance each day. If you borrowed $10,000 at a 12% APR, your daily interest charge is approximately $3.29.
  3. Daily charges are summed over your billing period. Over a 30-day month with a constant $10,000 balance, you’d accrue about $98–$99 in interest.

Some lenders use a 360-day year instead of 365 for this calculation, which slightly increases your effective daily rate. It’s worth confirming which method your lender uses before you sign.

Daily vs. monthly compounding

Some lines of credit compound interest monthly rather than daily, meaning interest accrues on unpaid interest from prior periods. Daily compounding is more common with online and alternative lenders; monthly compounding is more typical at traditional banks. 

Daily compounding results in a slightly higher effective rate over time — which is another reason APR is the cleanest comparison tool, since it already accounts for how compounding affects your true annual cost.

Fixed vs. variable rates on a business line of credit.

Most business lines of credit carry variable interest rates, meaning your rate can move up or down over the life of the line. Variable rates are typically tied to a benchmark like the prime rate (the rate banks use as a baseline for consumer and business lending) or the Secured Overnight Financing Rate, or SOFR (a widely used benchmark that replaced LIBOR for many commercial loan products). When those benchmarks rise, your interest rate rises with them — and so do your monthly payments on any outstanding balance.

Fixed-rate lines of credit are less common but available, particularly from traditional banks. A fixed rate means your interest cost stays the same no matter what happens in the broader market, which makes budgeting more predictable.

According to the Federal Reserve Bank of Kansas City’s Small Business Lending Survey, average rates for new business lines of credit in Q3 2025 were:

•      Variable-rate lines: 7.6%–7.9% (varying by urban vs. rural banks)

•      Fixed-rate lines: 7.0%–7.3%

Those figures reflect well-qualified borrowers at traditional banks. Rates from online and alternative lenders can run significantly higher — sometimes 30%–60% or more — depending on your credit profile and the lender’s underwriting criteria. That’s not a reason to avoid online lenders, but it is a reason to compare APRs carefully across all your options.

Fees that increase your total borrowing cost.

Interest isn’t the only cost to factor in. Business lines of credit often come with fees that can materially change what you pay to borrow, and not all lenders are upfront about them.

  • Draw fees are charged each time you pull funds from your line, typically 1%–3% of the amount drawn. On a $20,000 draw, a 2% draw fee adds $400 to your cost before interest even accrues.
  • Origination fees are charged when the line is first opened, usually 1%–3% of the total credit limit.
  • Annual or maintenance fees keep the line open even when you’re not actively borrowing. These typically run under $200 per year but add up over the life of the account.
  • Prepayment penalties are less common on lines of credit than on term loans, but worth asking about if you plan to pay down your balance quickly.

All of these fees should be factored into your APR comparison — which is exactly why APR, not the nominal rate, is the number to focus on.

What your business interest rate depends on.

Lenders evaluate several factors when setting your rate. Understanding them helps you see where you have room to negotiate — or where preparing more thoroughly before you apply can make a real difference.

  • Credit profile. Both your personal and business credit scores affect your rate. Higher scores typically unlock lower APRs, especially with traditional banks.
  • Business revenue and cash flow. Steady, documented revenue signals lower risk to lenders. Businesses with strong cash flow often qualify for more competitive rates.
  • Collateral. Secured lines of credit — backed by assets like inventory, receivables, or equipment — typically carry lower rates than unsecured lines, because the lender has recourse if you can’t repay.
  • Lender type. Bank rates tend to be lower but come with stricter qualification requirements. Online lenders are more accessible but price their additional risk into higher rates.
  • Credit limit and term. Larger credit limits and longer draw periods can mean higher rates, since they represent more exposure for the lender.

What people often get wrong about business line of credit interest.

A few misunderstandings come up consistently — and clearing them up early can save you from surprises down the road.

  • “A low interest rate means a low cost.” Not necessarily. A 7% rate with a 2% draw fee, $500 origination fee, and $150 annual fee can cost more in real terms than a 10% rate with no additional fees. Always calculate APR.
  • “I’m paying interest on my full credit limit.” No — interest only accrues on the amount you’ve drawn. The undrawn portion of your line carries no interest cost.
  • “Variable rate means my rate will definitely go up.” Variable rates move in both directions. When benchmark rates decline, your rate can drop too — as many borrowers saw during the Fed’s rate cuts in late 2025.
  • “APR and interest rate mean the same thing.” They don’t. Interest rate is the base cost to borrow; APR is the total cost including fees. Comparing interest rates without looking at APR is an apples-to-oranges comparison.

Example: Estimating interest on a $50,000 draw.

Say you draw the full $50,000 from your business line of credit at a 10% APR. Using the daily balance method:

  • Daily rate: 10% ÷ 365 = 0.0274%
  • Daily interest on $50,000: $50,000 × 0.000274 = $13.70/day
  • Monthly interest (30 days): approximately $411

Now say you pay back $10,000 in the first week. Your outstanding balance drops to $40,000, and your daily interest charge drops to roughly $10.96/day for the rest of the month. That partial payment meaningfully lowers your total interest for the period — without requiring you to pay everything off at once.

This is why paying down your line of credit quickly, even partially, reduces your total interest cost more effectively than waiting for scheduled payment dates.

Summary & Key takeaways.

Interest on a business line of credit accrues only on what you borrow, making it a flexible and potentially cost-efficient way to access working capital. The number that matters most is APR — not just the nominal interest rate — because APR reflects fees and gives you a true comparison across lenders. 

Most lines of credit use the daily balance method, and variable rates mean your cost of borrowing can shift over time. Paying down your balance quickly is one of the most effective ways to reduce total interest paid.

Lendio makes it easy to compare multiple lender offers tailored to your business — so you can see real terms side by side and move forward with confidence.

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