Statutory Interest Calculator - California

California does not use one rate for every claim type. For contracts without a specified rate, Cal. Civ. Code § 3289(b) sets ten percent (10%) per year simple interest from the date of breach or wrongful retention. Many non-contractual claims reference seven percent (7%) per year under Cal. Const. art. XV, § 1, subject to proof and procedural requirements. After judgment, Cal. Code Civ. Proc. § 685.010(a)(1) provides a ten percent (10%) post-judgment default, with a five percent (5%) rate for certain qualifying personal debt under fifty thousand dollars or medical debt under two hundred thousand dollars under § 685.010(a)(2)(A). The constitutional usury framework also caps many private loans at ten percent (10%) per year. Identify your claim type before quoting a single percentage in 2026.

The start date depends on the governing authority. Under Cal. Civ. Code § 3289(b), contract statutory interest typically runs from the date of breach or when payment was due and wrongfully withheld—often tied to invoice due dates or loan default notices in the documentary record. Tort prejudgment interest under Cal. Const. art. XV, § 1 and related code sections follows accrual rules specific to the harm and pleading. Post-judgment interest under Cal. Code Civ. Proc. § 685.020(a) generally begins on the date of entry of the money judgment, not the trial date. Partial payments credit against principal prospectively. Build a chronology of breach, demand, filing, and entry before using any calculator output in a demand letter or motion.

If your written contract specifies a permissible interest rate, that negotiated rate generally controls prejudgment contract interest so long as it complies with Cal. Const. art. XV, § 1 and related usury exemptions for regulated lenders. Cal. Civ. Code § 3289(b) applies when the contract is silent on interest or when statutory interest is otherwise appropriate for wrongful retention of money due. A twelve percent note, a zero percent invoice with statutory interest after default, and a judgment under § 685.010 are three different analytical paths. Courts will not apply § 3289(b) ten percent when a valid contract rate governs unless the clause is void or unenforceable. Compare your agreement text to § 3289(b) before assuming the statutory rate replaces your APR.

California statutory frameworks—including Cal. Civ. Code § 3289(b) and Cal. Code Civ. Proc. § 685.010—are expressed as simple annual rates on principal in routine planning. Interest does not automatically compound into principal each period unless a contract, court order, or specialized statute requires compounding. The constitutional and usury structure under Cal. Const. art. XV, § 1 likewise polices impermissible charges rather than authorizing open-ended compounding on statutory claims. This calculator models simple interest only: Interest equals principal times rate times years. If your instrument compounds, build a separate amortization schedule or consult counsel. Do not capitalize accrued interest into principal without legal authority.

Pre-judgment statutory interest compensates for delay before the court enters judgment—commonly ten percent (10%) per year under Cal. Civ. Code § 3289(b) for qualifying contract claims from breach, or seven percent (7%) per year under Cal. Const. art. XV, § 1 for many tort contexts. Post-judgment interest under Cal. Code Civ. Proc. § 685.010 runs on unpaid judgment principal after entry, typically ten percent (10%) with the five percent (5%) carve-out for defined consumer and medical judgments. The legal theories, start dates, and proof requirements differ even when the percentage matches. A demand letter citing § 3289(b) is not interchangeable with a post-judgment abstract citing § 685.010. Segment your timeline and rate for each phase.

Use simple interest unless a contract or order requires otherwise: Interest equals principal times annual rate times years. For the verified contract rate, twenty-five thousand dollars ($25,000) at ten percent (10%) for eighteen months equals three thousand seven hundred fifty dollars ($3,750) ($25,000 × 0.10 × 1.5). Partial periods may use daily accrual: principal times rate divided by three hundred sixty-five. Apply the seven percent tort reference only when that framework governs. After judgment, switch to § 685.010 and confirm whether the five percent category applies. TheLegalCalc multiplies principal, rate, and years you enter. Verify breach dates, payments, and judgment entry with a California attorney before filing or enforcing.