Crate br_financial 

br_financial

A Rust library for calculating real estate financing in Brazil.

Amortization Systems

• SAC (Sistema de Amortização Constante): Fixed amortization payments with decreasing total payments over time.
• Price (Sistema Francês de Amortização): Fixed total payments throughout the financing period (PMT calculated once upfront).

Additional Features

• Insurance: Monthly cost composed of a normalized rate applied to the outstanding balance plus a fixed fee (insurance_cost = balance * rate + fee).
• Administration fee: Fixed monthly amount added to each installment.
• Monetary correction: Variable monthly rate applied to the current balance before amortization. Rates are provided as a BTreeMap<NaiveDate, Decimal>, looked up by the most recent issue date on or before the installment due date.
• Date-based installments: Each payment has a due date computed from start_date, due_day (1–28), and month offset.
• Internationalization: Error messages localized via rust-i18n (EN and PT-BR).

Example

use std::collections::BTreeMap;
use br_financial::{calculate_debt_trajectory, DebtCalculationInput, DebtCalculationType, Locale};
use rust_decimal_macros::dec;
use chrono::NaiveDate;

let input = DebtCalculationInput {
    total_amount: dec!(360_000),
    interest_per_year: dec!(10.5),
    down_payment_percent: dec!(5),
    total_months: 420,
    debt_type: DebtCalculationType::Sac,
    insurance_rate: dec!(0.0003),
    insurance_fee: dec!(25),
    admin_fee: dec!(30),
    due_day: 15,
    start_date: NaiveDate::from_ymd_opt(2026, 1, 1).unwrap(),
    monthly_correction_rates: BTreeMap::new(),
    locale: Locale::En,
};

match calculate_debt_trajectory(input) {
    Ok(result) => {
        println!("Financed: {:.2}", result.financed_amount);
        println!("Total Paid: {:.2}", result.table.total_paid);
        println!("Total Insurance: {:.2}", result.table.total_insurance);
        println!("Total Admin Fees: {:.2}", result.table.total_admin_fees);
        println!("Total Monetary Correction: {:.2}", result.table.total_monetary_correction);
    }
    Err(e) => eprintln!("Error: {}", e),
}

Re-exports

pub use debt_calculator::DebtCalculationInput;

pub use debt_calculator::DebtCalculationType;

pub use debt_calculator::MonthPayment;

pub use debt_calculator::TableResult;

pub use debt_calculator::calculate_table;

pub use locale::Locale;

Modules

debt_calculator

locale

utils

Structs

DebtTrajectoryResult

Contains the comprehensive results for a financing calculation.

Functions

calculate_debt_trajectory

Calculates the debt trajectory for the selected amortization system.