Short answer. Determinate as to its kind, at the very least. Quantity may be left open, provided it can be worked out later without the parties having to make a fresh agreement. So a promise to sell "a portion of my land" is usually too vague to enforce; a promise to sell "my lot in Barangay X" is not.
What the law says
The object of every contract must be determinate as to its kind. The fact that the quantity is not determinate shall not be an obstacle to the existence of the contract, provided it is possible to determine the same, without the need of a new contract between the parties.
Civil Code, Article 1349 — Object Must Be Determinate. Read the full provision →
Kind must be fixed; quantity may be left open
The article separates two things people usually run together. Kind is what is being promised — land, rice, a specific vehicle, a defined service. That must be settled at the moment of contracting: The object of every contract must be determinate as to its kind. Quantity is how much of it, and the law is deliberately relaxed here. The fact that the quantity is not determinate shall not be an obstacle to the existence of the contract. That relaxation is what makes ordinary commerce possible. Requirements contracts, supply agreements pegged to a buyer's monthly needs, and construction work billed on actual measured output would all be impossible if every figure had to be nailed down in advance.
The real test: can it be worked out without a new deal?
The permission comes with a condition, and the condition is the whole point: quantity must be capable of being determined without the need of a new contract between the parties. Ask yourself whether, if the two of you stopped speaking tomorrow, a stranger with the document and the surrounding facts could arrive at the figure. If the answer is yes — because the contract supplies a formula, a rate, an external index, a measurable standard, or a reference to the buyer's actual consumption — the contract stands. If the answer is that you would have to sit down and negotiate again, then what you have is not a binding contract but an agreement to agree.
Where this bites in practice
Land is the usual battlefield. A deed selling "a 300-square-metre portion" of a larger untitled parcel, with nothing to say which 300 square metres, invites years of litigation, because the kind is clear but the thing itself is not identified. The cure is cheap and available before signing: a technical description, a lot number, boundaries, a sketch plan attached as an annex. The same discipline helps in service and supply agreements. Name the deliverable, name the standard it must meet, and name the method by which volume will be measured. Vagueness rarely favours the party who accepted it — it favours whoever ends up in possession.
What this article does not do
It addresses only how precisely the object must be described. It does not make an otherwise defective contract good. The object must still be within the commerce of man and not contrary to law or public policy; the parties must still have consented and had the capacity to do so; and certain contracts must still be in a particular form or be registered before they bind third parties. Nor does the article decide price, which is governed separately. Read the other way round, though, the message is reassuring: a contract does not fail merely because a number was left to be computed. It fails when nobody can say what was promised.
Cases citing this provision
These Supreme Court decisions cite the provision above. We list them so you can read them yourself; the summaries of what each decided are not ours to give.
- Aurora Fe B. Camacho vs. Court of Appeals, et al, G.R. No. 127520, February 9, 2007 — read the decision on LawPhil →
- Cristina R. Seming vs. Emelita P. Alamag, et al, G.R. No. 202284, March 17, 2021 — read the decision on LawPhil →
- Benito Marasigan, Jr. vs. Provincial Agrarian Reform Officer, Land Bank of the Philippines, G.R. No. 222882, December 2, 2020 — read the decision on LawPhil →
- Domingo Realty, Inc., et al. vs. Court of Appeals, et al, G.R. No. 126236, January 26, 2007 — read the decision on LawPhil →