Tools

Merger arbitrage spread calculator

Enter the deal terms and get the gross spread, annualized yield, market-implied probability of closing and expected value. Dividends and the withholding tax on them are handled, because most calculators quietly get that part wrong.

Deal terms

Tip: leave your own probability blank and the expected value uses the market-implied number, where it equals the current price by definition. Enter your own estimate to see your edge.

Assessment

Net upside per share
-
offer plus dividend, less withholding tax on the dividend
Gross spread
-
upside over the current price
Annualized yield
-
gross spread scaled to a year
Market-implied probability of close
-
priced by today's discount to upside
Expected value per share
-
probability-weighted upside and downside
Expected value vs current price
-
above 1.00 means positive expected value

For research and illustration. Not investment advice. Figures depend entirely on the inputs you provide.

How the numbers are computed

Net upside

Offer price plus any dividend you still collect before settlement, minus the withholding tax charged on that dividend. Taxing the offer price instead of the dividend, a common spreadsheet error, understates the upside.

Gross spread

The net upside over the current market price. It is the raw return if the deal closes at terms and you bought today.

Annualized yield

The gross spread scaled to a full year using the days to expected close. It is what makes a tight spread on a fast deal comparable to a wide spread on a slow one.

Implied probability

Rearranged from the current price: (current minus downside) divided by (upside minus downside). It is the probability of closing that today's price implies, assuming your downside estimate is right.

Expected value

The probability-weighted average of the upside and downside outcomes. Divided by the current price it gives the expected-value ratio, where anything above 1.00 is a positive-expected-value entry at today's price.

FAQ

Questions we get asked.

How do you calculate the merger arbitrage spread?

The gross spread is the net upside per share divided by the current market price. The net upside is the offer price plus any dividend collected before settlement, less the withholding tax on that dividend. Annualizing it means multiplying by 365 divided by the days to expected close.

Should the dividend be included in the arbitrage spread?

Yes, if the holder collects it before settlement it adds to the upside, but only net of the withholding tax charged on the dividend. Taxing the whole offer price instead of just the dividend is a frequent error that understates the real spread.

What does the implied probability of closing mean?

It is the probability of completion that the current price implies, computed as (current minus downside) divided by (upside minus downside). If your own probability estimate is higher than the implied one, the spread is compensating you more than the market thinks it should.

Is this the same math FPM uses?

Yes. The calculator runs the same assessment formulas that FPM computes server-side on every deal, so what you see here is a small slice of the product working on one situation.

This is one deal. FPM runs your whole book.

The calculator does the math for a single situation. FPM keeps every live deal as a structured record with this assessment computed automatically, the regulatory path per jurisdiction, and a full audit trail.

Merger arbitrage software The implied probability formula, explained