How Our Calculators Work

Formula: Future Cost = Current Cost × (1 + Rate / 100)^Years

Example: $400/mo groceries at 5.2% for 5 years ≈ $515.30

Compound growth applied to prices — same structure as investment returns.

Formula: Payment = P × [r(1+r)ⁿ] / [(1+r)ⁿ − 1]

Example: $10,000 at 6% for 3 years ≈ $304.22/mo

Standard amortization. Early payments are mostly interest.

Formula: M = P × [r(1+r)ⁿ] / [(1+r)ⁿ − 1]

Example: $250,000 at 4.5% for 30 years ≈ $1,266.71/mo

Same amortization math as other installment loans, larger scale.

Formula: FV = PV(1+r)ⁿ + PMT × [((1+r)ⁿ − 1) / r]

Example: $10,000 + $500/mo at 7% for 20 yrs ≈ $300,852

Lump sum plus regular contributions compounding together.

Formula: Nest egg via growth formula; guideline withdrawal ≈ Balance × 0.04

Example: $1,000,000 → ~$40,000/yr (4% rule planning start)

4% is a planning heuristic, not a guarantee.

Formula: Surplus = Income − Expenses; Savings Rate = Surplus / Income

Example: $4,500 − $3,500 = $1,000 surplus (~22%)

Clarity comes from seeing the split, not complex algebra.

Formula: Net Worth = Assets − Liabilities

Example: $350,000 − $200,000 = $150,000

One snapshot of position; track it over time.

Formula: PMT = FV × r / [(1+r)ⁿ − 1]

Example: $50,000 in 5 years at 3% ≈ $774/mo

Inverts growth math to find the contribution required.

Formula: Months Covered = Savings / Monthly Expenses

Example: $12,000 / $3,500 ≈ 3.4 months

Cushion measured in months of burn rate.

Formula: Savings Rate = Savings / Income × 100

Example: $21,000 / $75,000 = 28%

Strong predictor of long-term wealth building.

Formula: Tax ≈ Σ (income in bracket × bracket rate)

Example: Progressive layers — only the top slice faces the top rate

Illustrates marginal vs effective rates.

Formula: Compare cumulative rent vs ownership cost (payment, tax, equity, opportunity)

Example: Break-even horizon depends on rates, stay length, and appreciation

Planning comparison — not a purchase recommendation.

Formula: Amortize revolving balance at monthly APR; interest accrues on unpaid principal

Example: Minimum payments stretch payoff and multiply interest

Shows cost of carrying a balance.

Formula: A = P(1+r/n)^nt (+ contributions if any)

Example: Time dominates rate when contributions are steady

Visualizes compounding paths.

Formula: Payment capacity from income/DTI; back into sustainable price

Example: Higher rates shrink affordable price quickly

Guideline only — lenders use full underwriting.

Formula: Standard installment amortization on vehicle principal

Example: Term and rate drive total interest more than buyers expect

Compare cash vs financed total cost.

Formula: Balance_t+1 = (Balance_t − Withdrawal) × (1+r)

Example: Sequence-of-returns risk can exhaust the same average return early

Stress-tests sustainability of a withdrawal plan.

Formula: Installment amortization; optional prepayment shortens term

Example: Extra principal payments cut interest first

Educational estimate of payoff path.

Formula: Compare FV of all-in invest vs equal periodic buys

Example: Lump sum often wins mathematically; DCA can win behaviorally

Illustration of two funding styles.

Formula: Need − existing coverage = gap (simplified)

Example: Life/disability needs scale with income and dependents

Screening tool, not a policy quote.

Formula: Project assets/liabilities with savings rate and growth assumptions

Example: Small rate differences compound into large gaps over decades

Scenario sketch for trajectory.

Formula: FIRE number ≈ Annual spend / Safe withdrawal rate

Example: $40,000 / 0.04 = $1,000,000

Classic independence math as a planning target.