SumLoft
Run the numbers
Loans, savings, retirement

How long will it take to pay it off, save it up, or retire?

Loan payoff, retirement and savings-goal calculators that show every step of the arithmetic, alongside plain-English guides to the formulas behind them. Every figure is illustrative, and nothing you enter leaves your browser.

Loan payoff calculator

See how an extra monthly payment shortens the payoff timeline and cuts the interest.

Standard amortization, month by month. Illustrative only, not a quote.

Payoff dateApr 204610 years early
Interest saved$118,38339% less interest
Total interest$185,762vs $304,145 scheduled

Balance over time

With the extra paymentScheduled

Paying an extra $300 a month cuts around 10 years from this loan.

The tools

Three calculators, one method

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  1. 01Loan payoffYears and interest cut by an extra monthly paymentOpen →
  2. 02Retirement projectionBalance at retirement and the income it could supportOpen →
  3. 03Savings goalThe monthly amount that reaches a goal on timeOpen →
  1. You enter numbersYour real balances, rates and timelines.
  2. We apply the formulasStandard amortization and compound-growth math.
  3. We model timeMonth by month, so extra payments and growth show up.
  4. You get an estimateFor education, private by default. Nothing is stored.
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Money walkthrough80 guidesMoney worksheet2 guides
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The guides to read first

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  1. 01Money walkthroughCompound Interest Formula: The Power of Compound InterestCompound interest formula explained: A = P(1 + r/n)^(nt) variable by variable, worked examples, continuous compounding, and the power of compound interest.
  2. 02Money walkthroughHow to Make a Budget (7 Steps That Actually Stick)This worksheet builds a budget in seven steps: add up take-home pay, categorize spending, pick a method, set limits, save first, automate, and review monthly.
  3. 03Money walkthroughHow to Build an Emergency Fund (6 Steps)How to build an emergency fund in six steps: set a target, hit a starter goal, open the right account, automate the transfer, and replenish it after use.
  4. 04Money walkthroughHow to Calculate Net Worth: The Step-by-Step FormulaHow to calculate net worth, step by step: list what you own, value each line fairly, total what you owe, subtract, and read the result on a sample statement.
  5. 05Money walkthroughHow Much Do I Need to Retire at 55? The Real NumberHow much do I need to retire at 55? A walkthrough of the target multiple, the answer matrix pairing spending with years left, and the coverage decade to 65.
  6. 06Money worksheetHow to Calculate Your Retirement Number: The Formula (5 Steps)This worksheet gives you the formula for retirement: your number step by step, from annual spending to a monthly savings target, without a salary mistake.
Newest first

Guides that show the math

All walkthroughs →
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Newest walkthrough

Credit Utilization Ratio Explained: The Formula

This walkthrough explains credit utilization ratio: the formula, per-card versus overall utilization, the commonly cited 30 percent target, and lowering it.

25 min read
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How to Find Your Social Security Benefit Estimate Online

This worksheet shows how to find your Social Security benefit estimate online in 8 steps, from a verified account to reading the earnings record behind it.

25 min
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Social Security Pay Chart by Birth Year, Explained

This walkthrough turns a Social Security pay chart by birth year into a mechanism: your bend point year, illustrative figures, and a built-in calculator.

25 min
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What Is a Good Credit Score? Ranges Explained

This walkthrough explains what is a good credit score: the commonly cited FICO bands, the five factors behind it, and what each range tends to unlock.

25 min
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How Much Car Can You Afford? An Income-Based Rule

This walkthrough prices car affordability from your income, a commonly cited rule of thumb, loan term tradeoffs, and a worked example with your own numbers.

25 min
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How Much Down Payment Do You Need for a House?

This walkthrough prices a house down payment by percentage tier, what PMI costs below 20 percent, closing costs, and the monthly saving to reach your target.

25 min
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72(t) SEPP Rule Explained: Early Withdrawals, No Penalty

72(t) SEPP payments let you tap an IRA or 401(k) before 59 and a half without the early withdrawal penalty, if you lock into a fixed, unbending schedule.

28 min
A person typing on a laptop showing a simple two-panel chart under investing-themed headings, with a small cash jar and three stacked cubes marked with rising arrows on the desk beside itMoney walkthrough

What Is Dollar-Cost Averaging? How It Works

Dollar-cost averaging means investing a fixed amount on a set schedule regardless of price: how it works, the average-cost math, and when a lump sum wins.

26 min
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Asset Allocation by Age: Stocks vs Bonds

This walkthrough covers asset allocation by age: the common rule-of-thumb formulas, the stocks-versus-bonds math, glide paths, and a worked drawdown example.

25 min

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A calculator you understand beats one you just trust.

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Every calculator is paired with a guide that explains the formula and the assumptions, so the answer is legible, not magic.

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At the time of writing this site carries no affiliate links and no advertising. No link earns a commission and no company pays for coverage. If that ever changes, the disclosure page will say so first and any paid link will be marked where it appears.

SumLoft is an educational tool. Every result is an illustrative estimate built on the assumptions you enter, not financial advice. Rates, tax rules and contribution limits change, so confirm the current figures and talk to a qualified financial professional before acting on any number.

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