Household Budget

Monthly budget with income, taxes, expenses, savings goals, and the 50/30/20 rule.

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Where does your paycheck actually go? This walkthrough builds a monthly budget for a two-income household, tracking income through taxes, fixed and variable expenses, savings goals, and a 50/30/20 rule health check. Along the way you’ll see CalcMark’s currency arithmetic, percentage calculations, and rate conversions in action.

The complete CalcMark file is available at testdata/examples/household-budget.cm.

Income #

Start with gross salaries. CalcMark’s $ currency literal tags values as US dollars, and adding two currency values preserves the unit.

gross_salary_1 = $6500
gross_salary_2 = $5200
total_gross = gross_salary_1 + gross_salary_2

total_gross evaluates to $11,700. Currency arithmetic works just like plain numbers – the dollar sign carries through every operation.

CalcMark features: Currency literals ($); currency addition.

Tax Withholding #

Tax rates are plain decimals. Multiplying a currency value by a decimal produces a currency result, so you can compute taxes without losing the $ unit.

Estimated combined effective tax rates:

federal_rate = 0.18
state_rate = 0.05
fica_rate = 0.0765

total_tax_rate = federal_rate + state_rate + fica_rate
total_taxes = total_gross * total_tax_rate
net_income = total_gross - total_taxes

The combined rate is 0.3065 (about 30.7%), giving total_taxes = $3,586.05 and net_income = $8,113.95.

CalcMark features: Decimal arithmetic; currency multiplication and subtraction; markdown prose between calculations.

Fixed Expenses #

Fixed expenses stay the same each month. List them individually, then sum them up. CalcMark handles long addition chains cleanly.

These don't change month to month:

rent = $2200
car_payment = $450
car_insurance = $180
health_insurance = $400
phone_plans = $120
internet = $80
streaming = $45

total_fixed = rent + car_payment + car_insurance + health_insurance + phone_plans + internet + streaming

total_fixed comes to $3,475. Each line item is a named variable you can reference later – for example, streaming reappears in the 50/30/20 analysis below.

CalcMark features: Currency literals; variable references in expressions; multi-operand addition.

Variable Expenses #

Variable expenses fluctuate month to month. Use estimates based on past spending and sum them the same way.

Estimates based on past spending:

groceries = $800
gas = $250
utilities = $150
dining_out = $300
entertainment = $200
personal_care = $100
household_supplies = $150

total_variable = groceries + gas + utilities + dining_out + entertainment + personal_care + household_supplies

total_variable evaluates to $1,950. Keeping variable expenses separate from fixed expenses lets you see where you have room to cut.

CalcMark features: Currency addition; named variables for later reuse.

Savings Goals #

Savings are not expenses – they’re transfers to future-you. Defining them as their own category makes the budget easier to reason about.

emergency_fund_contribution = $500
retirement_401k = $600
vacation_fund = $200

total_savings = emergency_fund_contribution + retirement_401k + vacation_fund

total_savings is $1,300 per month. You’ll use this value in the health check and emergency fund sections below.

CalcMark features: Currency addition; forward references via named variables.

Summary #

Now pull everything together. Subtract total outflow from net income to see what’s left over each month.

total_expenses = total_fixed + total_variable
total_outflow = total_expenses + total_savings
remaining = net_income - total_outflow

total_expenses is $5,425, total_outflow is $6,725, and remaining is $1,388.95. That leftover amount is your buffer for unexpected costs or additional saving.

CalcMark features: Currency arithmetic; derived calculations referencing earlier variables.

Budget Health Check #

Express each category as a percentage of net income. Dividing currency by currency produces a plain number, which you can multiply by 100 for a percentage.

Calculate percentages of net income:

savings_rate = total_savings / net_income * 100
fixed_pct = total_fixed / net_income * 100
variable_pct = total_variable / net_income * 100

savings_rate is about 16.02, fixed_pct is about 42.83, and variable_pct is about 24.03. These percentages give you a quick snapshot of where your money goes.

CalcMark features: Currency division producing plain numbers; percentage calculations.

The 50/30/20 Rule Check #

The 50/30/20 rule is a popular budgeting guideline. You can reclassify your expenses into needs, wants, and savings, then check the split against the targets.

The 50/30/20 rule suggests:
- 50% on needs (fixed + essential variable)
- 30% on wants (discretionary)
- 20% on savings

needs = total_fixed + groceries + gas + utilities
wants = dining_out + entertainment + personal_care + streaming
savings_check = total_savings

needs_pct = needs / net_income * 100
wants_pct = wants / net_income * 100
savings_pct = savings_check / net_income * 100

needs_pct lands around 47.7%, wants_pct around 7.95%, and savings_pct around 16.02%. Needs are under the 50% ceiling. Wants are well below 30%, which means there is room to redirect more toward savings to hit the 20% target.

CalcMark features: Markdown prose (including bullet lists) between calculations; mixing variables from different sections.

Emergency Fund Status #

How many months could your emergency fund cover? Divide the balance by monthly expenses. Then calculate how long it takes to reach the recommended six-month target.

Current emergency fund balance:

current_emergency = $8500
monthly_expenses = total_fixed + total_variable
months_runway = current_emergency / monthly_expenses
target_months = 6
target_fund = monthly_expenses * target_months
shortfall = target_fund - current_emergency
months_to_goal = shortfall / emergency_fund_contribution

months_runway is about 1.57 – roughly six weeks of coverage. The six-month target_fund is $32,550, leaving a shortfall of $24,050. At $500/month, months_to_goal is about 48 months (four years).

CalcMark features: Currency division producing plain numbers; goal planning with derived variables.

Daily Discretionary #

CalcMark’s rate conversion syntax lets you express monthly costs as daily amounts. The per day keyword converts a monthly rate without accumulating it.

Per-day discretionary spending as a rate:

daily_dining = $300/month per day
daily_entertainment = $200/month per day
daily_discretionary = $500/month per day

$300/month per day divides by ~30.44 days, giving about $9.86/day for dining out. Seeing spending at the daily level makes it easier to evaluate impulse purchases.

CalcMark features: Rate literals ($300/month); rate per unit for rate conversion.

Features Demonstrated #

This example showcases the following CalcMark features:

• Currency literals – $ symbols for US dollar values
• Currency arithmetic – addition, subtraction, multiplication, division
• Decimal arithmetic – plain numbers for tax rates and percentages
• Named variables – reusable values referenced across sections
• Percentage calculations – dividing currency by currency for ratios
• Rate literals – $300/month, $200/month
• Rate conversion – $300/month per day to convert time units
• Markdown prose – headings, paragraphs, and bullet lists between calculations
• Template interpolation – {{variable}} to embed computed values in prose

Try It #

cm testdata/examples/household-budget.cm