Financial concept · 2 min read

Understanding IRR (Internal Rate of Return)

What IRR means, how to read it against your discount rate, and exactly which cells compute it in the original A1 — Cow Bid Price and Budget spreadsheet.

What It Is

IRR is the annualized rate of return an investment is expected to generate. More precisely, it's the discount rate at which the investment's cash flows — the money out now, the money in over time — net out to a Net Present Value of exactly zero.

Put simply: it's the break-even interest rate for the deal. If money actually cost you that rate to borrow, this purchase would neither make nor lose you anything in present-value terms.

How to Read It

Compare IRR to your discount rate — your cost of capital, or what you could otherwise earn on that money.

↑ IRR higher than your discount rate — the investment returns more than your money would earn elsewhere. NPV is positive. Good deal.

↓ IRR lower than your discount rate — the investment returns less than your money's opportunity cost. NPV is negative. The price is too high.

Discount rate

5.0%

IRR

−1.7%

Using the spreadsheet's own default numbers ($1,300 bid price): IRR sits well below the 5% discount rate, so the tool reports "Bid too high." (The spreadsheet itself shows −6.4%; see "One thing worth knowing" below for why the web tool gives −1.7%.)

Where It Lives in the Excel

Sheet "1. Cow Bid Price" of A1 — Cow Bid Price and Budget.xlsx

In the spreadsheet

B64Calculates IRR: =ROUND(IRR(B51:I51,+B63),3)*100

B63Starting guess fed to the IRR solver

B51:I51The Year 0–7 cash flow series IRR is solved over

B55Turns B64 into the sentence you read on screen

In the web tool

Result panel"IRR" stat tile, next to NPV and Payback, with the no-loan IRR under it

LiveRecalculates instantly as you move the bid price or any other input

NarrativeSame sentence as B55, written out below the tiles

One Thing Worth Knowing

Spreadsheet error, fixed in the web tool The cash flow series the Excel feeds into IRR() (B51:I51) has already been discounted by the discount rate earlier in the sheet. An IRR has to be solved on the raw, undiscounted cash flows, so the spreadsheet's IRR comes out too low (−6.4% instead of −1.7% with its own numbers). Since November 4, 2026 the web tool solves the IRR on the undiscounted flows: the down payment in year 0 (or the whole bid price with no loan), then each year's net cash flow after the loan payment, plus the cull cow sale in the last year.

With a loan, the IRR is a return on the down payment When part of the cow is financed, year 0 is only your down payment (20% by default), and the loan payments come out of the later years. So the IRR measures the return on the cash you put in, not on the cow. A cheap loan makes it look much higher than the cow's own return. That's why the tool also shows the IRR of buying the same cow outright, with no loan.

How It Fits with NPV and Payback

The Result panel shows all three together because each answers a slightly different question.

IRR

What annualized rate of return does this deal actually produce?

NPV

In today's dollars, how much value (or loss) does this deal create at your chosen discount rate?

Payback

How many years until the cumulative cash flows turn positive?