Z-spread (Zero-Volatility Spread)
Computes a bond's Z-spread: the constant spread added to the entire zero (spot) rate curve so the present value of its cashflows equals the market price. Unlike the nominal spread, which uses a single point, it accounts for the whole shape of the curve; for an option-free bond the Z-spread equals the OAS. Enter the cashflow times and amounts, the zero rate at each node and the price; the result is in basis points.
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Z-spread (Zero-Volatility Spread)
Computes a bond's Z-spread: the constant spread added to the entire zero (spot) rate curve so the present value of its cashflows equals the market price. Unlike the nominal spread, which uses a single point, it accounts for the whole shape of the curve; for an option-free bond the Z-spread equals the OAS. Enter the cashflow times and amounts, the zero rate at each node and the price; the result is in basis points.
Z-spread of a bond over the spot curve
Two bonds from the same issuer, different coupons, maturities a few months apart โ and the G-spread quoted off a single point on the curve says one is cheaper. The Z-spread cuts through that. It is the constant spread, in basis points, you add to the entire zero (spot) curve so the present value of the cash flows lines back up with the market price. Rather than measuring yield against one Treasury vertex, it spreads the discounting across every tenor. Credit analysts and fixed-income desks reach for it to compare bonds with unlike cash-flow shapes on a consistent footing.
The mechanics are a root search. Each cash flow is discounted at its tenor's zero rate plus the spread z โ Price = ฮฃ CFi / (1 + ri + z)ti โ and the calculator nudges z by bisection until the summed present values equal the price you entered. Because z shifts every vertex at once, it is a parallel add-on to the curve, not a point-by-point adjustment. One caveat worth keeping: for an option-free bond the Z-spread equals the OAS, but once there is a call, put, or prepayment feature, the Z-spread still carries the cost of that optionality โ stripping it out takes an OAS model, which this tool does not run.
Enter each cash flow's tenor, its amount, the zero rate at each vertex, and the market price. The output comes back in basis points and represents the constant premium the market demands above that bond's risk-free curve. A quick sanity check: feed it the present value of the flows discounted on the bare curve as the price, and the Z-spread should land near zero; a price below that value pushes the spread up, a price above it sends the spread negative. Also confirm the zero-rate tenors line up with the cash-flow dates you supplied.
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The results provided by this tool are for general informational and educational purposes only and do not constitute professional, financial, medical, legal, tax or accounting advice. Always confirm important decisions with a qualified professional and official sources.