Spades Bags & Bidding Calculator
Score a Spades hand and see what an overtrick really costs — minus nine points, not plus one — and how much confidence bidding one higher needs.
Score a hand
A bag is not worth +1. It is worth −9.
Take a trick past your bid and you get a point for it. Collect 10 of them and you lose 100. So ten bags earn +10 and then cost −100 — ninety points down, for an average of -9 points per overtrick, exactly, at any length of season.
| Overtricks in a session | Points from them | Each |
|---|---|---|
| 5 | 5 | 1.0 |
| 10 | -90 | -9.0 |
| 20 | -180 | -9.0 |
| 40 | -360 | -9.0 |
| 100 | -900 | -9.0 |
Which reframes the game. Ten overtricks over an evening cost 90 points; being set on a four-bid costs an 80-point swing. A quiet habit of taking one extra trick a hand is more expensive than a disaster you would actually remember — and nobody blames the bags.
And the more you have bid, the surer you must be to bid one more
Suppose you will take either n or n+1 tricks, and n+1 with probability p. Bid low and the extra trick is a bag; bid high and you either make it or you are set for double. Setting the two expectations equal gives p* = (20n + 10) / (20n + 29) — which is not a constant. It climbs:
| Bidding | Confidence you need | |
|---|---|---|
| 1 → 2 | 61.2% | |
| 2 → 3 | 72.5% | |
| 3 → 4 | 78.7% | |
| 4 → 5 | 82.6% | |
| 5 → 6 | 85.3% | |
| 6 → 7 | 87.2% | |
| 7 → 8 | 88.8% | |
| 8 → 9 | 89.9% |
The reason is that being set costs twice the bid — you take −10n instead of +10n — so the downside grows with the contract, while the bag you avoid is a flat −9 however big the hand. A player using one rule of thumb for every hand is bidding too high on the big ones and too low on the small ones: a flat 75% rule is wrong on 6 of the 8 steps in one direction and 2 in the other.
How to use
- Enter your bid, the tricks you took, and the bags you already had.
- Read what the hand is really worth once the penalty is amortised.
- Check the confidence you would have needed to bid one higher.
- Compare a habit of overtricks against a single failed contract.
Frequently asked questions
What is a bag really worth in Spades?
Minus nine points. An overtrick pays one point tonight, but ten of them cost a hundred, so ten bags earn plus ten and then lose a hundred — ninety points down, nine per bag, exactly, at any length of session.
Are overtricks in Spades bad?
Yes, badly. Ten overtricks over an evening cost ninety points, while being set on a four-bid costs an eighty-point swing. A quiet habit of taking one extra trick a hand is more expensive than a disaster you would actually remember, and nobody ever blames the bags.
How confident should I be before bidding one more?
It depends on how much you have already bid, and the answer climbs. Going from one to two needs about sixty-one per cent, three to four needs seventy-nine, and eight to nine needs ninety. One rule of thumb cannot fit the whole range.
Why does the required confidence go up with the bid?
Because being set costs twice the bid — you take minus ten times it instead of plus ten times it — so the downside grows with the contract. The bag you avoid by bidding higher is worth a flat minus nine however big the hand, so the two sides scale differently.
What is the formula for the break-even bid?
If you will take n or n plus one tricks, and the higher figure with probability p, the two bids are worth the same when p equals twenty n plus ten, divided by twenty n plus twenty-nine. Below that, bid low; above it, bid high.
How does the bag penalty work?
Each trick past your bid adds one bag. When the count reaches ten, a hundred points come off and the counter resets to zero rather than carrying the excess forward, so the eleventh bag starts a fresh count.
What happens if you break a nil bid?
You lose a hundred instead of gaining one, and the tricks you took still count as bags on top. A broken nil is therefore worse than the two hundred point swing suggests.
Does this send anything anywhere?
No. Everything is worked out in your browser and nothing is stored or uploaded.
🔒 This tool runs entirely in your browser. Nothing you enter is uploaded, logged, or stored.