Line of Credit Sizing

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Line of Credit Sizing Calculator

What Is a Business Line of Credit?

A business line of credit is a revolving credit facility that allows a company to borrow up to a set limit, repay it, and borrow again as needed. Unlike a term loan, which is a fixed amount borrowed for a specific purpose, a line of credit is designed to manage short-term cash flow gaps — the timing difference between when you pay your costs and when you collect your revenue.

For contractors, a line of credit is one of the most important financial tools available. Construction cash flow is inherently lumpy — costs go out before billings are submitted, billings are submitted before payment is received, and retainage sits with the owner for months after the work is done. A properly sized line of credit smooths those gaps without forcing the business to carry excess cash as a permanent reserve.

Why Line of Credit Sizing Matters

Most contractors approach their bank and ask for a line of credit without a clear rationale for the amount they are requesting. They pick a round number — $500,000 or $1,000,000 — based on gut feel or what they think they can get approved. The problem with this approach is twofold.

An undersized line creates a false sense of security. A contractor who secures a $300,000 line and then takes on a $2,000,000 project may find the line fully drawn and exhausted at precisely the moment they need it most — mid-project, with costs running and collections lagging.

An oversized line costs money unnecessarily. Most commercial lines of credit carry an unused commitment fee — typically 0.25% to 0.50% per year on the undrawn balance. A $1,000,000 line that never draws above $300,000 is paying $1,750 to $3,500 per year in unused fees for capacity that is never needed.

The right line size is the one that covers your peak borrowing need with a reasonable cushion — no more, no less.

What Drives Line of Credit Need

Three factors determine how large a line of credit a contractor needs.

Peak Cash Flow Gap

The maximum working capital deficit at any point in a given project or across your portfolio of active projects simultaneously. This is the most direct driver of line size. The Cash Flow Gap Calculator on this site can help you estimate the peak gap for individual projects.

Seasonal Working Capital Swing

Seasonal cash flow patterns in construction are driven by two overlapping forces that non-construction businesses don't experience in the same way.

The first is weather-driven work volume. In most of the country, construction activity ramps up in spring, peaks in summer, and slows significantly in fall and winter. During the ramp-up period — typically March through June — contractors are mobilizing crews, purchasing materials, and incurring costs on new projects before the billing and collection cycle catches up. This creates a cash deficit that builds through the early busy season even as revenue is growing.

The second force is project lifecycle timing. Large projects that started in spring are typically in their heaviest billing months by midsummer, which helps cash flow. But as those projects close out in fall, retainage is released — providing a cash inflow — while new project starts slow down. The result is a cash position that often looks strong in late fall as retainage comes in, then deteriorates again in late winter when the pipeline is thin and the next season's work hasn't started yet.

The practical implication is that a contractor's worst cash position is often in late winter or very early spring — after the previous season's work has been collected and before the new season's billings are generating meaningful cash. This is precisely when a line of credit needs to be available, and precisely when a contractor who has been drawing on the line all winter may find it at or near its limit.

To estimate your seasonal working capital swing, compare your average monthly cash balance at its seasonal low point — typically February or March — against your average monthly cash need at your seasonal peak — typically June or July. The difference between those two points is your seasonal swing. If your cash balance is typically $150,000 in February and you typically need $400,000 available to fund peak-season operations in June, your seasonal swing is $250,000.

Emergency and Opportunity Reserve

A line of credit should have capacity beyond your expected peak draw to handle unexpected cash needs — a disputed receivable that delays collection, an equipment failure requiring immediate replacement, or an opportunity to take on additional work that requires upfront mobilization costs. A reserve of 20% to 30% above your expected peak draw is a reasonable target.

The Formula

Recommended Line Size = Peak Cash Flow Gap + Seasonal Working Capital Swing + Reserve

Where: Reserve = (Peak Cash Flow Gap + Seasonal Working Capital Swing) x Reserve Percentage

A Worked Example

A specialty contractor reviews their cash flow across their typical project mix and seasonal pattern:

Peak cash flow gap on largest active project: $380,000 Additional gap from two smaller concurrent projects: $140,000 Total peak project gap: $520,000

Seasonal working capital swing (difference between winter low and summer peak cash need): $180,000

Combined peak need: $520,000 + $180,000 = $700,000

Reserve at 25%: $700,000 x 0.25 = $175,000

Recommended line size: $700,000 + $175,000 = $875,000

This contractor should be discussing a line of credit in the $850,000 to $900,000 range with their bank — not a $500,000 line because that seemed reasonable, and not a $1,500,000 line because bigger felt safer.

What Banks Look At

Knowing your line size need is the starting point. Getting it approved is a separate conversation. Banks evaluate line of credit requests based on several factors.

Accounts receivable quality. Most commercial lines are secured by accounts receivable. Your borrowing base — the amount the bank will advance against eligible receivables — may be lower than your line limit. A $900,000 line with an 80% advance rate against $800,000 in eligible receivables gives you $640,000 in actual availability, not $900,000. Understanding your borrowing base before you approach the bank helps you set realistic expectations. The Borrowing Base Calculator on this site can help you estimate your availability.

Debt service coverage. The bank will evaluate whether your cash flow is sufficient to service any existing debt plus the expected interest on the line. A line of credit that is never fully paid down begins to look like a term loan in the bank's eyes, which raises questions about your ability to service it. Lenders generally want to see the line paid to zero at least once during the year as evidence that it is being used for short-term cash flow purposes rather than as permanent working capital.

Business financial strength. Your balance sheet net worth, your profitability trend, and your overall leverage all factor into the bank's decision. A contractor with a strong balance sheet and consistent profitability gets better terms and a higher limit than one with thin equity and volatile earnings.

Revisiting Your Line Size Annually

Your line of credit need changes as your business grows. A contractor doing $5 million in revenue needs a different line than one doing $15 million. Review your line size annually — ideally before your renewal conversation with the bank — and come in with a documented rationale for any increase you are requesting. A banker who sees a clear, numbers-based explanation for why you need a larger line is far more likely to approve it than one who hears "we've grown and need more."