Consideration is the doctrine that separates an enforceable contract from an empty promise. It is the first thing a professor probes when the class is asked whether a contract even exists — and it is the element students most often misapply because they confuse whether a deal was fair with whether it was bargained for. This page gives you the rule, the way courts apply each piece, worked examples, and the exam trap that costs points every year.

What is consideration in contract law?

Consideration is the bargained-for exchange that makes a promise legally enforceable. Under the modern Restatement (Second) of Contracts § 71, a performance or return promise is consideration if it is (1) sought by the promisor in exchange for the promise and (2) given by the promisee in exchange for that promise. Put simply: each side must give up something of legal value, and that thing must be the price of the other's promise. A promise supported by consideration is enforceable; a promise unsupported by it — like a promise to make a gift — generally is not.

The two elements you must prove

Every consideration analysis breaks into two parts. Miss either and there is no consideration.

1. Legal value (legal detriment or benefit). The promisee must incur a legal detriment — doing something they were not legally obligated to do, or forbearing from something they were legally entitled to do — or the promisor must receive a legal benefit. A promise, an act, or a forbearance can all supply value.
2. Bargained-for exchange. The value must be sought by the promisor in exchange for the promise and given by the promisee in exchange for the promise. This is the inducement requirement: the promise induces the detriment, and the detriment induces the promise. Each is the reason for the other.

The classic illustration of both elements working together is Hamer v. Sidway (N.Y. 1891), where an uncle promised his nephew $5,000 if the nephew refrained from drinking, smoking, swearing, and gambling until age 21. The court held there was consideration: the nephew gave up a legal right (he was legally entitled to do those things), and that forbearance was the exact thing the uncle bargained for. The uncle received no economic benefit — that did not matter. Legal detriment to the promisee is enough.

How courts apply each requirement

Legal value: detriment, not economic loss

The value requirement is about legal detriment, not whether someone actually came out worse economically. Giving up a legal right you were free to exercise — even a right you would never have exercised — counts. This is why the nephew's abstinence in Hamer was consideration even though quitting smoking arguably helped him.

Bargained-for exchange: the inducement test

This is where most gift promises die. Ask: was the detriment the price of the promise, or was it merely a condition attached to a gift? The famous hypothetical is the promise, 'If you come around the corner to my shop, I'll give you a coat.' Walking around the corner is a detriment, but it was not bargained for — the promisor did not seek your walk as the price of the coat; walking was just a condition of receiving a gift. No consideration.

Adequacy is not sufficiency

Courts do not police whether the exchange was fair. A peppercorn can be consideration for a car. Adequacy — economic equivalence — is not required; the court only checks legal sufficiency (whether legal value was bargained for). The exception: a purely nominal or sham recital ('in consideration of $1') that everyone knows was never intended as a real bargain may be disregarded as a pretense.

The things that are NOT consideration (memorize these)

Every issue-spotter tests at least one of these. When a promise looks unenforceable, one of these is usually why.

1. Past consideration. An act already performed before the promise was made cannot be consideration, because it could not have been bargained for in exchange for a promise that did not yet exist. 'You saved my life last week, so I promise to pay you $500' — generally unenforceable. (Some jurisdictions and the Restatement § 86 recognize a limited 'material benefit' or moral-obligation exception; flag it, don't assume it.)
2. Pre-existing legal duty. Doing (or promising to do) something you are already legally bound to do is not consideration. A contractor who demands more money to finish a job he is already contractually obligated to complete gives no new consideration for the extra pay (the traditional rule; note that UCC § 2-209 abolishes this requirement for modifications of contracts for the sale of goods, and even at common law a modification may be enforceable if unanticipated circumstances arise).
3. Illusory promise. A 'promise' that leaves the promisor free to do whatever they want — reserving unlimited discretion to perform or not — is no promise at all and cannot be consideration. 'I'll buy as many widgets as I want from you' is illusory. But requirements and output contracts (UCC § 2-306), and promises where the discretion is limited by good faith or a reasonable-efforts obligation, are NOT illusory.

Worked examples

Example 1 — valid consideration. Ana promises to pay Ben $2,000 if Ben paints her fence, and Ben promises to paint it. Each promise induces the other; Ben incurs a legal detriment (labor he was not obligated to give); Ana bargained for that labor. Enforceable.

Example 2 — gift, no consideration. Uncle Sam tells his niece, 'When you graduate, I'll give you my old car.' The niece graduates. Graduating is a condition, not the bargained-for price of the car — Uncle Sam sought no return for his gift. No consideration; the promise is unenforceable as a contract (though promissory estoppel may rescue it).

Example 3 — pre-existing duty trap. A ship crew is hired for a voyage. Mid-voyage, some sailors desert, and the captain promises the remaining crew extra wages to complete the trip they are already bound to complete. Traditional rule: no consideration, because finishing the voyage was a pre-existing duty (Stilk v. Myrick). Watch for the modification exception when circumstances have genuinely and unexpectedly changed.

The exam trap that costs points

The single most common error is treating adequacy and bargained-for exchange as the same thing. Students see an unfair or lopsided deal and write 'no consideration because the exchange was unequal.' Wrong — courts do not weigh adequacy. Conversely, students see a clear detriment and stop there without asking whether it was bargained for, missing the gift-promise problem. Discipline yourself: (1) identify the legal value, then (2) separately ask whether it was the price of the promise. Two steps, always both.

The second trap: when consideration is genuinely missing, weaker exam answers stop and say 'unenforceable.' Strong answers pivot to promissory estoppel (Restatement § 90) — a promise the promisor should reasonably expect to induce reliance, that does induce definite and substantial reliance, is enforceable to the extent necessary to avoid injustice, even without consideration. Gift promises that fail for lack of consideration frequently survive on reliance. Always run the § 90 backup.

Related doctrines and how they interact

• Promissory estoppel (§ 90) — the primary consideration substitute; picks up where the bargain requirement fails but reliance exists.
• Mutuality of obligation — the requirement that both parties be bound; illusory promises fail here because one side is not really bound.
• Contract modification — where the pre-existing duty rule lives; know the common-law rule, the unforeseen-circumstances exception, and UCC § 2-209 (no new consideration needed for good-faith modifications of goods contracts).
• Moral obligation / material benefit rule (§ 86) — the narrow exception that can enforce a promise made in recognition of a past benefit.
• Option contracts and firm offers (UCC § 2-205) — situations where offers become irrevocable with or without consideration.

Putting it together

On an exam, walk consideration in this order: (1) Is there legal value — a detriment, forbearance, or return promise? (2) Was it bargained for — did each side's promise induce the other's? (3) Trap check — is this past consideration, a pre-existing duty, or an illusory promise? (4) If consideration fails, is there promissory estoppel? Hit those four beats and you have handled the doctrine the way the professor wants it handled.