Alternate Lines Calculator
One line in, fair odds at every alternate half point out.
| Spread | Fair % | Push % | Lay it | Take it |
|---|---|---|---|---|
| -9 | 32.6% | 2.0% | +195 | -234 |
| -8.5 | 34.0% | — | +183 | -219 |
| -8 | 34.7% | 2.3% | +177 | -211 |
| -7.5 | 36.2% | — | +166 | -197 |
| -7 | 38.0% | 4.7% | +153 | -182 |
| -6.5 | 40.9% | — | +135 | -159 |
| -6 | 42.2% | 3.0% | +128 | -151 |
| -5.5 | 43.9% | — | +119 | -140 |
| -5 | 44.8% | 2.1% | +115 | -135 |
| -4.5 | 46.0% | — | +109 | -128 |
| -4 | 47.2% | 2.6% | +104 | -122 |
| -3.5 | 48.6% | — | -102 | -115 |
| -3your line | 52.4% | 7.3% | -120 | +102 |
| -2.5 | 55.8% | — | -139 | +118 |
| -2 | 57.1% | 2.2% | -146 | +124 |
| -1.5 | 58.0% | — | -152 | +129 |
| -1 | 59.3% | 2.2% | -161 | +136 |
| -0.5 | 60.2% | — | -167 | +142 |
| 0 | 61.7% | 2.5% | -179 | +151 |
| +0.5 | 62.7% | — | -187 | +158 |
| +1 | 64.0% | 2.1% | -199 | +167 |
| +1.5 | 64.7% | — | -206 | +173 |
| +2 | 66.1% | 2.0% | -219 | +183 |
| +2.5 | 66.7% | — | -227 | +189 |
| +3 | 71.3% | 6.3% | -286 | +234 |
"Lay it" is your price on the favourite side of that number, "take it" is your price on the underdog side. The pair carries the width you set, so at 4% the two quoted probabilities add to about 104%. Notice how much the price moves across a key number compared with an ordinary one: that gap is the whole reason alternate lines are not evenly spaced.
Enter one spread, the fair price you believe belongs on it, and the width you want to quote. The calculator derives two-sided prices at every half point around your number, so you can post a whole ladder from a single opinion.
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How the Alternate Lines Calculator works
How alternate lines are priced from one number
Your spread and price define a view: at that number, this side covers this often. The calculator finds the margin distribution consistent with that view, then reads the cover probability off it at every other half point. Every rung comes from the same opinion, so the ladder is internally consistent rather than a set of independent guesses.
Why the rungs are not evenly spaced
Football margins pile up on 3 and 7, so the probability gap between -2.5 and -3.5 is far larger than the gap between -10.5 and -11.5. A ladder built on a smooth curve would misprice exactly the numbers that matter most. This one carries the same key-number clustering used by the compare lines calculator.
What market width means, and why it is the maker’s lever
Width is the total margin across both sides of your quote. At 4% the two prices you post imply about 104% between them, and that 4% is your theoretical hold. Tighter widths attract more volume and leave less cushion; wider widths do the reverse. It is the main lever a maker actually controls.
Pushes and whole numbers
On a whole number there is a real chance of landing exactly on it, which is a push rather than a win or a loss. The fair percentages here are conditional on the bet resolving, and the push column shows how much of the outcome space is being set aside. That is why whole numbers price so differently from the half points beside them.
A worked NFL ladder around -3
An NFL favourite laying 3 at a fair coin flip, quoted at 4% width. Read down the fair column and watch what happens either side of 3: the step from -3.5 to -2.5 moves roughly seven percentage points, while the step from -6.5 to -5.5 moves about three. That is the entire argument for pricing alternate lines off a real margin distribution instead of a smooth curve.
| Spread | Fair % | Push % | Lay it | Take it |
|---|---|---|---|---|
| -6 | 39.9% | 2.9% | +141 | -166 |
| -5.5 | 41.7% | — | +131 | -154 |
| -5 | 42.6% | 2.1% | +126 | -148 |
| -4.5 | 43.8% | — | +120 | -141 |
| -4 | 44.9% | 2.6% | +114 | -134 |
| -3.5 | 46.4% | — | +107 | -126 |
| -3 | 50.0% | 7.3% | -108 | -108 |
| -2.5 | 53.6% | — | -126 | +107 |
| -2 | 54.8% | 2.2% | -133 | +113 |
| -1.5 | 55.8% | — | -139 | +118 |
| -1 | 57.1% | 2.2% | -146 | +124 |
| -0.5 | 58.0% | — | -152 | +129 |
| 0 | 59.5% | 2.5% | -163 | +138 |
How this is modelled. Margins are treated as a normal distribution around your line, reweighted by how often each exact margin actually occurs, using the same per-league key numbers as the compare lines calculator. The NFL weights come from the published 2000-2025 margin distribution. These are documented approximations rather than exact constants, so treat the ladder as a well-grounded starting point you would sanity-check against a live market, not a finished price sheet.
To check two specific numbers against each other, use the compare lines calculator. To see the margin a width implies, use the hold calculator, and to strip width back out of a quoted pair, use the no-vig calculator.
Frequently asked questions
What is a market making calculator?+
It turns one reference line into a full set of alternate lines. You supply a spread, the fair price you think belongs on it, and the width you want to quote, and it returns two-sided prices at every half point around that number.
How do you price alternate lines?+
Work out the probability the bet covers at each alternate number using a margin distribution anchored to your reference line, then convert those probabilities to odds and add your market width across the two sides.
What is a good market width?+
It depends on how much volume you want and how much risk you will carry. Retail books commonly run 4 to 5% on a standard spread market. Tighter than that attracts more action with less cushion for being wrong.
Why do prices jump so much around 3 in the NFL?+
Because roughly one NFL game in seven ends with a 3-point margin. Moving a line across 3 shifts far more probability than moving it across a number where results rarely land, so the price has to move much further.