From Restitution to Quantification.
Ideally, the quantification of damages should be instinctive and superfluous: it is sufficient to provide the victim with what is needed to restore them to the situation they would have been in without the damage (for example, an equivalent sum of money to compensate for financial loss or an identical item to replace a damaged one).
For this reason, restitution in kind is prioritized when possible.
However, in many circumstances, it is not possible. For example, in cases of unlawful expropriation, the property from which the victim has been deprived may have been destroyed for reasons of public interest. In such cases, it is appropriate to substitute restitution in value, in the form of equivalent monetary compensation.
The quantification of damages and interest fundamentally corresponds to the calculation of the value restitutions that the judge should grant as damages to restore the balance before the harmful acts (as of the judgment date).
As an exception, in recent years in French law, the quantification of certain damages is based on the undue gains made by the wrongdoers.
Not all damages are reparable.
In accordance with Article 1240 of the Civil Code, the harm, also called recoverable damage, results from any “fault” causing harm to others, whether this fault directly targets the victim of the damage or the victim is indirectly affected by a fault inflicted on a third party.
In other words, harm arises only under three cumulative conditions: the existence of a fault, the existence of harm, and the existence of a causal link between the fault and the harm.
Beyond their prohibitive absence, these three elements determine the nature of the damages. The nature of the fault, in particular, influences the extent of the harm.
Thus, the damage resulting from a fault falling under contractual liability (for example, a contractual breach) is limited by its foreseeability, at least in its nature if not in its amount. On the other hand, the damage resulting from a fault falling under tort liability is not subject to such a limit.
Of course, this rule, applicable in French law, is not necessarily applicable, or not to the same extent, in foreign law. For example, Belgian law strictly reserves the limit of foreseeability for the nature of the damage (and not for its amount).
Furthermore, the repairable nature of damage also depends on the absence of force majeure, the limitation periods (five years from the wrongful event for commercial matters in French law), or – regarding contractual disputes – any limitation clauses for damages and their validity.
Thus, the quantification of damages must take into account these different limits.
Not all damages are quantified in the same way.
Finally, bodily, economic, and moral damages must be quantified differently.
The first are generally assessed based on fixed scales, while the latter are based on jurisprudence (except for moral damages of companies, which can be calculated as economic damages).
Economic damages, on the other hand, must be quantified by the plaintiff, their lawyer, or their private expert based on the economic and financial documentation at their disposal and in accordance with the methodologies applicable to different faults.