Cernarus

Budget Calculator

This budget calculator helps you compare your actual monthly spending to recommended allocation frameworks (50/30/20, zero‑based budgeting) and to custom percentage targets. Enter your gross monthly income and recurring category amounts to see totals, gaps, and suggested next steps.

Use the different methods to explore tradeoffs: the 50/30/20 rule provides a quick target split for needs, wants, and savings; zero‑based budgeting shows unallocated dollars that should be assigned; and custom allocation lets you set your own target percentages.

Updated Nov 21, 2025

Allocates 50% of income to needs, 30% to wants, and 20% to savings/debt reduction. Compares each allocation to your entered categories to show gaps.

Inputs

Results

Updates as you type

Needs recommended (50%)

$2,500.00

Wants recommended (30%)

$1,500.00

Savings recommended (20%)

$1,000.00

Actual needs (entered)

$2,500.00

Actual wants (entered)

$250.00

Actual savings (entered)

$500.00

Needs gap

$0.00

Wants gap

-$1,250.00

Savings shortfall

$500.00

OutputValueUnit
Needs recommended (50%)$2,500.00currency
Wants recommended (30%)$1,500.00currency
Savings recommended (20%)$1,000.00currency
Actual needs (entered)$2,500.00currency
Actual wants (entered)$250.00currency
Actual savings (entered)$500.00currency
Needs gap$0.00currency
Wants gap-$1,250.00currency
Savings shortfall$500.00currency
Primary result$2,500.00

Visualization

Methodology

Calculations use straightforward arithmetic based on your entered monthly amounts. All percentage allocations are applied to gross monthly income unless stated otherwise.

This tool is an estimator intended for planning and education. It is not a substitute for professional financial advice. For security and reliability design guidance, computations and UI follow general best practices consistent with NIST digital identity and usability recommendations and ISO/IEEE interface guidance where applicable.

Outputs show both recommended allocation amounts and comparisons to your entered values so you can identify where to reassign dollars, increase savings, or cut discretionary spending. Data validation is limited to non‑negative numeric checks on inputs.

Worked examples

Example 1: Income $5,000; total expenses $4,200. Surplus $800 (16% of income). Under 50/30/20, savings target = $1,000; if current savings are $500, savings shortfall = $500.

Example 2: Income $3,000; after assigning categories your zero‑based unallocated = -$200 (shortfall). Actions: increase income, reduce discretionary categories, or reassign planned savings temporarily.

Further resources

External guidance

Expert Q&A

How accurate is this calculator?

This calculator produces estimates based on the numbers you enter. It does not model taxes, irregular income, or one‑time expenses unless entered. Results should be used for planning, not as definitive financial advice.

Which method should I use?

Use the actual budget method to understand current cash flow. Use 50/30/20 for a simple target split. Use zero‑based budgeting to ensure every dollar has a purpose. Use custom allocation to set personalized targets. Choose the method that fits your planning goals.

Do you account for taxes and pre‑tax deductions?

Inputs assume gross monthly income. If you prefer, enter net (take‑home) income instead and treat outputs as percentages of take‑home pay. For formal tax or benefit impacts consult a tax professional.

Can I track irregular or annual expenses?

Yes. Convert annual or irregular costs to monthly equivalents before entering (annual cost ÷ 12). The calculator treats all inputs as monthly amounts.

Is my data stored or shared?

This tool is a client‑side estimator. Follow the hosting site's privacy practices. For enterprise deployments follow NIST and ISO guidance for data protection and secure UI design.

Sources & citations