financial-calculator（金融计算器）

Financial Calculator

Comprehensive financial calculations including future value, present value, discount/markup pricing, compound interest, and comparative tables.

Quick Start

CLI Usage

# Future Value
python3 scripts/calculate.py fv 10000 0.05 10 12
# PV=$10,000, Rate=5%, Years=10, Monthly compounding

# Present Value
python3 scripts/calculate.py pv 20000 0.05 10 12
# FV=$20,000, Rate=5%, Years=10, Monthly compounding

# Discount
python3 scripts/calculate.py discount 100 20
# Price=$100, Discount=20%

# Markup
python3 scripts/calculate.py markup 100 30
# Cost=$100, Markup=30%

# Future Value Table
python3 scripts/calculate.py fv_table 10000 0.03 0.05 0.07 --periods 1 5 10 20
# Principal=$10,000, Rates=3%,5%,7%, Periods=1,5,10,20 years

# Discount Table
python3 scripts/calculate.py discount_table 100 10 15 20 25 30
# Price=$100, Discounts=10%,15%,20%,25%,30%

Web UI

Launch the interactive calculator:

./scripts/launch_ui.sh [port]
# Default port: 5050
# Opens at: http://localhost:5050
# Auto-creates venv and installs Flask if needed

Or manually:

cd skills/financial-calculator
python3 -m venv venv  # First time only
venv/bin/pip install flask  # First time only
venv/bin/python scripts/web_ui.py [port]

Features:

• 7 calculator types with intuitive tabs
• Real-time calculations
• Interactive tables
• Beautiful gradient UI
• Mobile-responsive design

Calculators

1. Future Value (FV)

Calculate what an investment will be worth in the future with compound interest.

Use cases:

• Investment growth projections
• Savings account growth
• Retirement planning

Inputs:

• Principal amount
• Annual interest rate (%)
• Time period (years)
• Compounding frequency (annual/quarterly/monthly/daily)

2. Present Value (PV)

Calculate the current value of a future amount (discounted value).

Use cases:

• Loan valuation
• Bond pricing
• Investment analysis

Inputs:

• Future value
• Annual discount rate (%)
• Time period (years)
• Compounding frequency

3. Discount Calculator

Calculate final price after applying percentage discount.

Use cases:

• Retail pricing
• Sale calculations
• Cost savings analysis

Inputs:

• Original price
• Discount percentage

Outputs:

• Discount amount
• Final price
• Savings percentage

4. Markup Calculator

Calculate selling price from cost and markup percentage.

Use cases:

• Product pricing
• Profit margin calculation
• Business pricing strategy

Inputs:

• Cost price
• Markup percentage

Outputs:

• Markup amount
• Selling price
• Profit margin (as % of selling price)

5. Compound Interest

Detailed breakdown of compound interest calculations.

Use cases:

• Interest analysis
• Effective rate comparison
• Loan interest calculation

Outputs:

• Final amount
• Total interest earned
• Effective annual rate

6. Future Value Table

Generate comparison table across multiple rates and time periods.

Use cases:

• Investment scenario comparison
• Rate shopping
• Long-term planning

Features:

• Add multiple interest rates
• Add multiple time periods
• View all combinations in sortable table
• See total gain and gain percentage

7. Discount Table

Compare multiple discount percentages for the same price.

Use cases:

• Bulk pricing strategies
• Promotional planning
• Price comparison

Features:

• Add multiple discount percentages
• See all discount scenarios
• Compare final prices and savings

Installation

Requires Python 3.7+ and Flask:

pip install flask

Or with venv:

python3 -m venv venv
source venv/bin/activate
pip install flask

Python API

Import the calculation module:

from calculate import (
    future_value,
    present_value,
    discount_amount,
    markup_price,
    compound_interest,
    generate_fv_table,
    generate_discount_table
)

# Calculate FV
fv = future_value(
    present_value=10000,
    rate=0.05,  # 5% as decimal
    periods=10,
    compound_frequency=12  # Monthly
)

# Generate table
table = generate_fv_table(
    principal=10000,
    rates=[0.03, 0.05, 0.07],  # As decimals
    periods=[1, 5, 10, 20]
)

Formulas

See references/formulas.md for detailed mathematical formulas, examples, and use cases for all calculations.

Tips

Rate Format:

• CLI: Use decimals (0.05 for 5%)
• Web UI: Use percentages (5 for 5%)
• Python API: Use decimals (0.05 for 5%)

Compounding Frequencies:

• 1 = Annual
• 4 = Quarterly
• 12 = Monthly
• 365 = Daily

Table Generation: Best practices for meaningful comparisons:

• FV tables: Use 3-5 rates, 4-6 time periods
• Discount tables: Use 5-10 discount percentages
• Keep tables focused for easier analysis

Performance:

• Web UI calculations are instant
• Tables with >100 combinations may take a few seconds
• CLI is fastest for single calculations

Common Workflows

Investment Planning

1. Use FV Calculator to project single investment
2. Generate FV Table to compare different rates
3. Check Compound Interest for detailed breakdown

Pricing Strategy

1. Use Markup Calculator to set selling price
2. Generate Discount Table to plan promotions
3. Compare margins and final prices

Loan Analysis

1. Use PV Calculator to value loan
2. Check Compound Interest for total interest cost
3. Generate FV Table to compare loan terms