Cost of Capital Math: Debt, Warrant and Crossover Formulas

Worked example

These values come from the default term sheet: $1M raised on a $10M post money equity valuation, or borrowed at 11% APR over 36 months with 12 months interest only, 8% warrant coverage, a 1.5% fee and an exit at $30M in four years.

Values produced by the default inputs
Equity dilution	10%
Equity cost at a $30M exit	$3,000,000
Origination and legal fee	$15,000
Total interest over the term	$228,588
Warrant stake	0.8%$80,000 of warrants valued at exit: $240,000
Headline debt cost	$483,588fees plus interest plus warrants
Fully loaded debt cost	$1,483,588principal included
Crossover exit	$2.65Mabove this exit, debt is cheaper in dollars
Peak monthly debt service	$46,608

The formulas

Both paths, one exit

Everything is measured at the same projected exit valuation, so the comparison is dimensional.

01
Equity dilution is capital raised over the post money valuation.
$d = \frac{C}{V _{post}}$
02
The dollar cost of that dilution is your stake in the exit.
$Cost_{equity} = X \cdot d$
03
Amortizing payments use the standard annuity formula over the months that follow the interest only grace period.
$M = P \cdot \frac{r ( 1 + r ) ^{n}}{( 1 + r ) ^{n} - 1}$
04
Total interest is every payment minus the principal, across both the grace and amortizing phases.
$\sum Interest = (P \cdot r \cdot m_{IO}) + (n \cdot M - P)$
05
Warrants convert at the next round, so their cost is coverage times principal as a share of post money valuation, multiplied by the exit.
$Cost_{warrant} = X \cdot \frac{C \cdot w}{V _{post}}$
06
The headline debt cost is the sum of fees, interest and warrants.
$Cost_{debt} = F + \sum Interest + Cost_{warrant}$

Result

Setting the two costs equal gives the crossover exit, the point above which debt is cheaper in dollars:

X^{*} = \frac{F + \sum Interest}{d - \frac{C \cdot w}{V _{post}}}

The fully loaded variant adds every dollar of principal and any balance still outstanding at the exit date. It is reported separately because the headline formula, like most lender marketing, omits principal.

Assumptions and caveats

Same exit for both pathsA rate and a percentage are different units. The only honest comparison is dollar cost at one defined outcome.
Interest only, then amortizingInterest is paid monthly from month one. Principal amortizes on a standard annuity schedule after the grace period ends.
Fees are paid at closeOrigination and legal fees are deducted from proceeds, so a $1M facility with a 1.5% fee puts $985,000 to work.
Warrants are equityThey convert at the next priced round. The model values them at the exit valuation used for the equity path, so both sides are measured on the same basis.
No taxes or prepayment penaltiesInterest is not tax adjusted, and the model assumes the loan runs to maturity unless the exit arrives first.
Principal is not a fee, but it is not free eitherThe headline number matches market convention. The fully loaded number matches reality. Both are on the page.

Glossary

Venture debtalso: venture lending: A loan to a venture backed company, usually sized to a fraction of the last equity round, with a warrant kicker. Cash is paid from operations, it is not forgiving capital.
Warrant coverage: The equity kicker quoted as a percentage of the loan principal. 8% coverage on $1M means warrants over $80k of stock, converted at the next priced round, so it dilutes like equity.
Interest only periodalso: IO period: The grace window at the start of a loan where you pay interest but no principal. Longer grace lowers the early payment and concentrates principal repayment later.
Amortization: The schedule that repays principal over time. A fully amortizing loan spreads principal and interest across equal payments, so the balance reaches exactly zero at maturity.
Origination fee: An upfront lender fee, usually 1 to 3 percent of the facility, deducted at close together with legal costs. You borrow $1M and receive $985k.
Post money valuation: The value of the company after new money goes in: pre money plus the round. Dilution from an equity round is simply capital raised divided by the post money valuation.
Cost of capital: The total economic cost of a financing, measured in dollars at a defined exit, not just the interest rate or the dilution percentage.
Crossover exit: The exit valuation where debt and equity cost the same. Above it debt wins in dollar terms, below it equity does.
Payment to burn ratio: Peak monthly debt service divided by monthly gross burn. Above roughly 20%, a single missed quarter threatens a covenant breach.

This model vs. the rule of thumb

Question	Standard rule of thumb	What this model does	Why it changes the answer
Cost metric	Interest rate versus dilution percentage	Both paths priced in dollars at the same exit	A rate and a percentage are different units. The only honest comparison is dollar cost at a defined outcome.
Warrants	Ignored, or noted as small	Valued at the exit and shown as an ownership percentage	Warrants are the lender upside and your dilution. At a $30M exit an 8% coverage kicker can out cost three years of interest.
Principal	Omitted from the comparison	Shown twice: headline formula and fully loaded with principal	Equity never repays capital, debt always does. Omitting principal makes debt look cheaper than it is.
Exit dependence	One fixed exit assumption	Live sensitivity from $5M to $100M with the crossover marked	Debt is cheap in a modest exit and expensive in a huge one. A single number hides that trade off.
Cash strain	Not modelled	Peak monthly service against gross burn, with a 20% tripwire	Debt can be cheaper on paper and still kill the company by consuming the cash it was raised to protect.

Frequently asked questions

Why is the interest rate alone a bad way to compare venture debt to equity?

Because an 11% interest rate is not the cost of debt. The all in cost includes the origination and legal fees taken at close, the interest actually paid across the term, and the warrant kicker, which only becomes expensive if the company succeeds. Equity has no cash cost at all but permanently transfers a slice of every future outcome. Comparing a rate to a dilution percentage compares two different units.

What is warrant coverage and why is it a hidden cost?

Warrant coverage is the equity kicker lenders take on top of interest, quoted as a percentage of the loan principal. At 8% coverage on a $1M facility, the lender receives warrants over $80,000 of equity. They cost you nothing in cash, which is why they are easy to ignore, but they convert to shares at the next round and dilute you exactly like a small equity round. This model prices that stake at your projected exit valuation so it appears next to the cash costs.

Why does the headline cost formula exclude principal repayment?

Because principal is borrowed money returned, not a fee, and every debt comparison in the market excludes it. But equity capital never has to be repaid, so a genuinely comparable comparison must count every dollar of principal leaving the business through the exit date. This model shows both: the headline formula of fees plus interest plus warrants, and a fully loaded view that adds principal and any balance still outstanding at exit.

What is the crossover exit valuation?

The future exit value at which both financing paths cost exactly the same number of dollars. Below it equity is cheaper, above it debt is cheaper, because equity keeps costing you a percentage of every extra dollar of value while debt costs a fixed fee plus a small warrant percentage. The crossover is where those two lines intersect, and it is the single most useful number for deciding between the two.

What does the insolvency risk indicator flag?

A monthly debt payment above 20% of gross burn. Venture debt is cash consuming by design: interest is paid in cash from month one, and principal repayment begins when the interest only period ends. If the amortized payment crowds out a fifth of your operating budget, one bad quarter turns into a covenant breach or a forced down round. The indicator is a tripwire, not a prediction.

Is venture debt really non dilutive?

Almost never completely. Warrants are equity, so a facility with 8% coverage on a $1M loan dilutes you by roughly the same amount as selling $80,000 of equity at the same valuation, and you still repay the principal with interest. The honest framing is less dilutive and cash consuming rather than non dilutive. The model shows the warrant stake as a percentage of the company so the claim is measurable.

When does venture debt actually make sense?

When you have predictable revenue to service payments, a crossover exit that sits below your realistic outcome, and a need to extend runway between rounds without resetting your valuation. It is a poor fit for pre revenue companies: the payment to burn ratio and the warrant cost both get worse precisely when the company is least able to carry them.