Rally vs Side-Out Scoring Odds
What each scoring system does to an edge — and why serving first is worth six points under side-out and nothing at all under rally.
Both formats are modelled with one rally-winning chance that does not depend on who is serving. Real players usually serve better than they receive, which would widen the side-out figures further; this deliberately leaves that out so the comparison isolates the scoring system. Nothing is uploaded.
Under side-out scoring, the first serve is worth something
Only the serving side can score, so whoever serves first gets the first chance to convert. Between two identical players that head start is worth 6.3 points of win probability — 53.2% against 46.8%. Under rally scoring it is worth nothing at all, because every rally is a point regardless.
| Rallies won | Serving first | Receiving first | Side-out serve is worth | Rally |
|---|---|---|---|---|
| 50% | 53.2% | 46.8% | 6.33 pts | 0.00 pts |
| 52% | 63.5% | 57.4% | 6.12 pts | 0.00 pts |
| 55% | 77.2% | 72.1% | 5.09 pts | 0.00 pts |
| 60% | 92.1% | 89.5% | 2.63 pts | 0.00 pts |
| 65% | 98.2% | 97.3% | 0.86 pts | 0.00 pts |
The head start matters least to the player who needs it least: it falls from 6.3 points at even skill to 0.86 at the top of the table, because a strong enough player was going to get the serve back anyway.
And once that is averaged out, side-out still amplifies more
This comparison is easy to get wrong. Side-out looks more decisive at every skill level — but it is not even at even, so part of that gap is the serve rather than the format. Averaging over who serves first restores exactly 50% between equal players, and only then does the comparison mean anything. It survives: at 55% of rallies, side-out gives 74.6% against rally scoring's 68.7%.
| Rallies won | Rally scoring | Side-out, serve averaged | Difference |
|---|---|---|---|
| 50% | 50.0% | 50.0% | 0.00 pts |
| 52% | 57.7% | 60.4% | 2.73 pts |
| 55% | 68.7% | 74.6% | 5.93 pts |
| 60% | 83.6% | 90.8% | 7.17 pts |
| 65% | 93.1% | 97.8% | 4.62 pts |
Both formats amplify — a small rally edge becomes a larger game edge under either — but side-out amplifies harder, because a weaker player has to win the rally twice over to score: once to take the serve and again to convert it. Rally scoring gives every rally to whoever won it, which is closer to simply counting.
How to use
- Enter the share of rallies you win.
- Set the target the game is played to.
- Compare rally scoring against both side-out serve orders.
- Read the serve-averaged comparison, which is the fair one.
Frequently asked questions
What is the difference between the two systems?
Under rally scoring every rally is a point, whoever served. Under side-out scoring only the serving side can score, so winning a rally on the receiving end wins the serve rather than a point.
Is serving first an advantage?
Under side-out, yes — about six points of win probability between two identical players, because the first server gets the first chance to convert. Under rally scoring it is worth nothing at all, since every rally scores regardless.
Does that advantage last?
It shrinks as the skill gap grows, from about six points at even down to under one point for a clearly stronger player. A good enough player was going to win the serve back anyway, so the head start stops mattering.
Which system favours the better player?
Side-out, once the serve is averaged out. A weaker player has to win the rally twice over to score — once to take the serve and again to convert it — where rally scoring simply gives each rally to whoever won it.
Why average over who serves first?
Because otherwise the comparison is unfair. Side-out looks more decisive at every skill level, but part of that gap is the serve rather than the format. Averaging restores exactly 50% between equal players, which is the check that the two are being compared properly.
How much is the format itself worth?
Several points of win probability at a realistic edge. It is smaller than the difference between two players but larger than most people assume a bookkeeping choice could be.
Does this model serving skill?
Deliberately not. Both formats use one rally-winning chance that does not depend on who is serving, which isolates the scoring system. Real players usually serve better than they receive, which would widen the side-out figures further.
Does this send anything anywhere?
No. Every figure is computed in your browser, and nothing is uploaded or stored.
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