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 walkthrough62 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 →
A three-storey red brick institutional building with a gabled entrance and tall chimneys, seen across a wide green lawn with a path where several people are walkingMoney walkthrough
Newest walkthrough

457(b) Plan Distribution Rules, Limits, and Withdrawals

This explainer covers 457(b) plan distribution rules, who sponsors the plan, the governmental split, deferral limits, and the separation-from-service quirk.

32 min read
A hand turning a small metal dial on a wooden panel marked with a curved row of dotsMoney walkthrough

How to Fill Out a W-4 So You Don't Owe in April (7 Steps)

This worksheet shows how a W-4 turns into a withholding amount, why a second job under-withholds by default, and how to fix a refund or a bill that is wrong.

40 min
A hand turning a metal knob mounted on a wood panel, with small dots marking positions around itMoney walkthrough

How to Max Out Your 401(k) Before Year End (6 Steps)

This worksheet backs out the per-paycheck percentage that maxes out a 401(k) before year end, counting the pay periods left and guarding the employer match.

39 min
A white ceramic piggy bank on a pale wooden surface beside four stacks of coins that rise in height and a folded pile of banknotesMoney walkthrough

Retirement Withdrawal Order: Which Account to Tap First

This walkthrough covers retirement withdrawal order: why taxable money usually goes first, when bracket filling reverses it, and how RMDs override the plan.

32 min
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What Is a CD? How Certificates of Deposit Work

This explainer covers how a certificate of deposit works, the term for rate trade, early withdrawal penalties in months of interest, CD ladders and variants.

38 min
A calculator, a stack of printed pages and a mug of coffee on a sunlit wooden deskMoney walkthrough

How to Manage Money With a Partner

This walkthrough sets up money with a partner in nine steps: the first conversation, joint or separate accounts, a proportional bill split, a solo-spend rule.

42 min
Two adults sitting side by side at a wooden kitchen table with an open laptop, loose printed sheets and a notebook, one of them writing with a penMoney walkthrough

Retirement Account Beneficiary Rules Explained

This explainer covers retirement account beneficiary rules: why the form outranks your will, primary versus contingent, per stirpes, trusts, and reviews.

35 min
Four stacks of coins rising in height on a wooden surface beside the corner of a blank calendar grid, lit against a dark blue wallMoney walkthrough

What Are I Bonds? How Do I Bonds Work

This explainer covers how I bonds work: the two-part rate built from a fixed piece and a resetting inflation piece, the lock-up and forfeit, and who it suits.

40 min
Two pairs of brown-framed reading glasses, a compartmented pill organizer, a coiled black stethoscope, a blank spiral notepad with a silver pen and a stack of pale blue folders on a light wooden tableMoney walkthrough

Healthcare Costs in Retirement: How to Plan

This walkthrough prices healthcare costs in retirement across three separate phases: the pre-Medicare bridge, the Medicare years, and long-term care risk.

34 min

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How to read SumLoft

Tools that teach

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.

How we make money

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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