Money 4 Today — everyday money arithmetic

Money 4 Today — everyday money arithmetic | money4today.com

A paycheque splits into three buckets, a loan costs APR, and a savings account pays APY. Below: the 50/30/20 rule worked out on incomes of 2,000, 3,500 and 5,000 dollars, APR and APY compared at 3, 5, 10 and 24 percent, and 1,000 dollars compounded year by year to 30.

money4today.comRule of 72: 72 ÷ rate = years to double. At 6 percent, about 12 years.U.S. credit card APRs averaged above 20 percent in recent Federal Reserve data.

Key figures

After-tax income split by the 50/30/20 rule, and key rates referenced on this page.
After-tax income	Needs (50%)	Wants (30%)	Savings (20%)
$2,000 / month	$1,000	$600	$400
$3,500 / month	$1,750	$1,050	$700
$5,000 / month	$2,500	$1,500	$1,000
$24,000 / year	$12,000	$7,200	$4,800
$42,000 / year	$21,000	$12,600	$8,400
$60,000 / year	$30,000	$18,000	$12,000

After-tax income split by the 50/30/20 rule, and key rates referenced on this page.

Figures at a glance

Each table below is reproduced from the sections; the arithmetic is yours to check.

Dates behind the figures

The key terms of this guide, drawn to one scale

What does 50/30/20 mean on a real paycheque?

Take after-tax income, multiply by 0.50, 0.30 and 0.20 — that is the whole rule.

Elizabeth Warren and Amelia Warren Tyagi set out the 50/30/20 rule in their 2005 book All Your Worth. The starting number is what lands in your account after tax, not your gross salary. Needs cover rent, utilities, groceries, insurance and minimum debt payments. Wants cover dining out, subscriptions and upgrades. Savings is the 20 percent that goes to an emergency fund, retirement accounts or extra debt payoff.

The rule is a default, not a law. If rent alone eats 45 percent of take-home pay, the split will not balance in one month; the point is to see the imbalance and move one bucket at a time.

Needs: housing, utilities, groceries, transport, insurance, minimum payments.

Wants: restaurants, streaming, travel, gadgets, hobbies.

Savings: emergency fund, retirement contributions, extra principal payments.

How to work through it, step by step

What does APR actually cost me?

APR is the yearly cost of a loan including fees, expressed as a percentage — the number lenders must disclose under the U.S. Truth in Lending Act of 1968.

APR tells you one year of borrowing cost on the amount you still owe, with origination fees folded in. On a credit card, recent Federal Reserve data put average APR above 20 percent; on a mortgage or car loan the rate is typically far lower. The gap is the difference between revolving short-term debt and secured long-term debt.

The Consumer Financial Protection Bureau, created in 2011, publishes plain-language explainers of APR and credit costs. Reading the APR disclosure before signing is the cheapest form of comparison shopping: two offers with the same monthly payment can differ by hundreds of dollars in total cost once fees are included.

Ask for APR, not just the monthly rate — monthly rate × 12 understates the cost.
Check whether fees are inside the APR; the Truth in Lending Act requires disclosure.
Compare the same loan term: a lower APR over a longer term can still cost more.

How does compound interest change 1,000 dollars?

Interest added back to the principal earns its own interest — 1,000 dollars at 5 percent compounded annually reaches about 1,276 dollars in 5 years and 1,629 dollars in 10.

Simple interest pays only on the original principal. Compound interest pays on principal plus previously earned interest, so the curve bends upward. At 3 percent the same 1,000 dollars reaches about 1,344 dollars in 10 years; at 8 percent it reaches about 2,159 dollars. The rate difference looks small on paper and large over decades.

The rule of 72 estimates doubling time without a calculator: 72 divided by the interest rate. At 6 percent, money doubles in about 12 years; at 3 percent, about 24 years; at 12 percent, about 6 years. The rule is an approximation, accurate enough for planning, not for tax filing.

Why keep the emergency fund in cash, not investments?

A common target is three to six months of essential expenses, in an account reachable without selling investments.

An emergency fund exists to be spent quickly and without loss. Money tied up in stocks or long-term deposits forces a sale at whatever price the market offers that day. The three-to-six-month target is measured against essential expenses — rent, food, utilities, insurance — not against total take-home pay.

The savings bucket of the 50/30/20 rule is where this fund starts. Once it holds several months of essentials, the same 20 percent can move to longer-term accounts without changing the budget split.

Count essential monthly expenses, not average spending.
Multiply by 3 for a minimum target, by 6 for a conservative one.
Hold it where it can be withdrawn in days, not months.

Common questions

Do I apply 50/30/20 to gross or take-home pay?

Take-home pay. The rule divides after-tax income, so multiply your net monthly deposit by 0.50, 0.30 and 0.20 to get three dollar amounts.

Why is my savings account APY higher than its APR?

Because APY includes compounding and APR does not. A 5.00 percent APR account with monthly compounding pays about 5.12 percent APY.

Is the rule of 72 exact?

No, it is an approximation. It is accurate enough for planning: at 6 percent money doubles in about 12 years, at 3 percent in about 24.

How big should my emergency fund be?

Three to six months of essential expenses, held in an account reachable without selling investments.