Proportionality is a general principle in law which covers several separate concepts:

• The concept of proportionality is used as a criterion of fairness and justice in statutory interpretation processes, especially in constitutional law, as a logical method intended to assist in discerning the correct balance between the restriction imposed by a corrective measure and the severity of the nature of the prohibited act.
• Within criminal law, the concept is used to convey the idea that the punishment of an offender should fit the crime.
• Under international humanitarian law governing the legal use of force in an armed conflict, proportionality and distinction are important factors in assessing military necessity.
• Under the United Kingdom's Civil Procedure Rules, costs must be "proportionately and reasonably incurred", or "proportionate and reasonable in amount", if they are to form part of a court ruling on costs.