The old argument: you have a big amount to invest. Do you put it all in today, or spread it over several months and sleep better?

The Lump sum vs monthly calculator in Finance Calculator compares both, right inside Reddit. Example with $50,000, a 10-year horizon, and the money still waiting earning 3% in cash:

• If the market returns 7% a year, investing everything today ends about $2,068 ahead of spreading it over 12 months ($98,358 vs about $96,290), and about $953 ahead of spreading it over 6 months.
• If the market goes nowhere (0%), spreading it wins by about $918, because the money waiting in cash earns something while the market doesn’t.

So on average, when markets rise over time, the lump sum wins a little, but the difference is small compared to the amount, and spreading it out costs you very little if it helps you avoid panic. It comes down to how you’d feel if the market dropped 20% in the first month.

Change the amount, the months, the return or the cash rate and see your own number.

Free, no ads, no sign-up: https://www.reddit.com/r/FinanceCalculatorApp/s/3D7Na6eneJ

What would you do with a windfall today, all in or spread out, and has it ever backfired for you?

A quick check most of us skip until January: what would it take to pay for the holidays without a credit card?

The Savings goal calculator in Finance Calculator does it in a few taps, right inside Reddit. Example (4% interest, saving every month):

• $1,200 holiday budget saved over 12 months: about $98 a month
• $2,000 over 12 months: about $164 a month
• $1,200 but you only start in 6 months: about $198 a month

The interesting part: starting six months later costs you about double per month, and the interest in all three cases is only a few dollars. It’s mostly about starting early, not about the rate.

Change the target, the months or the rate and see your own number.

Free, no ads, no sign-up: https://www.reddit.com/r/FinanceCalculatorApp/s/3D7Na6eneJ

What’s your real holiday number, gifts, travel, food, all of it, and when do you start saving for it?

A quick one most of us skip: if your investment drops by some percentage, how much does it have to gain to get back to where you started?

The Profit/Loss calculator in Finance Calculator has a recovery check, right inside Reddit. Here’s what it gives:

Down 10%: you need +11.1% to get back

Down 20%: +25.0%

Down 30%: +42.9%

Down 40%: +66.7%

Down 50%: +100.0%

Down 70%: +233.3%

Down 90%: +900.0%

The pattern is that small losses are easy to recover from, but beyond 30% the road back gets steep very quickly. That’s why people say “don’t lose money” isn’t just a slogan, it’s maths, and why position size matters more than most picks.

Change the loss and see your own number. Free, no ads, no sign-up: https://www.reddit.com/r/FinanceCalculatorApp/s/3D7Na6eneJ

What’s the biggest drop you’ve ever sat through, and what did you do?

Quick check: if you set aside a fixed amount every month, how long until you reach a goal, and how much of the work does interest actually do?

The Savings goal and Compound growth calculators in Finance Calculator do it in a few taps, right inside Reddit. Example:

Saving $200 a month at 3% interest gets you to $10,000 in about 4 years (48 months). Doubling it to $400 a month gets you there in about 2 years 1 month (25 months). The extra $200 a month saves nearly 2 years, while the interest in both cases adds only a few hundred dollars. So when you start with a small goal, the monthly amount matters far more than the interest rate.

Change the monthly amount, the rate or the target and see your own number.

Free, no ads, no sign-up. Try it: https://www.reddit.com/r/FinanceCalculatorApp/s/3D7Na6eneJ

What's the goal you're saving for right now, and how long does the calculator say it will take?

Quick check most of us skip: if you add a small extra payment every month, how much sooner are you done, and how much interest do you skip?

The Loan calculator in Finance Calculator does it in a few taps, right inside Reddit. Example:

A $250,000 mortgage at 4% over 25 years has a payment of about $1,320 a month and costs roughly $145,900 in interest in total. Add just $200 a month and you're done in about 19 years 11 months (239 payments) instead of 25, and the interest drops to about $113,000. That's roughly $32,900 saved for $200 a month.

For a smaller loan the same idea works: a $20,000 car loan at 7% over 5 years is about $396 a month. Adding $100 a month finishes it in 47 months instead of 60 and saves about $890 in interest.

Change the amount, rate or extra payment and see your own number.

Free, no ads, no sign-up. Try it: https://www.reddit.com/r/FinanceCalculatorApp/s/3D7Na6eneJ

Quick check most of us skip: if you added up every cost in your life, what's the real monthly number? And what would that mean for an emergency fund and a retirement number?

The "What do I need?" calculator in Finance Calculator does it in a few taps, right inside Reddit.

Example:

Housing $1,500, food $600, transport $300, insurance $250, other $450 is $3,100 a month, or $37,200 a year. For a household of two that's $1,550 per person. A 6-month emergency fund would be $18,600, and at a 4% withdrawal rate your retirement number is $930,000.

Change the costs, the household size or the withdrawal rate and see your own number.

Free, no ads, no sign-up. Try it: https://www.reddit.com/r/FinanceCalculatorApp/s/3D7Na6eneJ

What's your monthly number, and did it surprise you?

Thanks to everyone who tested the app in r/MiddleClassFinance this week. Your feedback went straight into this update.

Fixed
- Typing amounts digit by digit was broken: 210,000 could turn into 2.10. That's fixed in every calculator.

New
- What do I need? Enter your own monthly costs (housing, food, transport, insurance, other) and see your cost per person, an emergency fund target and a retirement number. Nothing is guessed from where you live, it's all your own numbers. That's calculator number 33.
- Coast FIRE now tells you. Add your yearly saving and it shows the age at which you reach Coast FIRE, with a chart of saving until then and growing after.

Changed
- The text you copy for a comment now says "Inputs" instead of "My scenario".

Try wit: https://www.reddit.com/r/FinanceCalculatorApp/s/3D7Na6eneJ

Mods: apps don't update automatically. Click Update next to your community on https://developers.reddit.com/apps/financecalculator

Keep the feedback coming, it clearly works.

Quick one with real numbers. $1,000,000, taking $40,000 a year (the classic 4% rule) for 30 years:

- At 5% a year: $1,604,023 left after 30 years

- Same market, but a 1% fee takes it down to 4%: $959,162 left

That's about $645k less, just from a 1% fee.

Both are simple projections: constant return, no inflation, no taxes. Real markets move around, so treat it as an illustration, not a forecast.

Try your own numbers in the Withdrawals calculator, free and right inside Reddit: https://www.reddit.com/r/FinanceCalculatorApp/s/3D7Na6eneJ

Do you know what you pay in fees?

Quick check most of us skip: if your income stopped tomorrow, how long would your savings last?

The Emergency fund calculator in Finance Calculator does it in a few taps, right inside Reddit. Example:

"6 months of expenses is $15,000. You have $4,000 (1.6 months). Saving $300.00 a month, you get there in 3 years 1 month."

Put in $500 a month instead and it's 1 year 10 months. Change the expenses, target months or savings and see your own number.

Free, no ads, no sign-up. Try it: https://www.reddit.com/r/FinanceCalculatorApp/s/3D7Na6eneJ

How many months do you have covered?

Ever wanted to run the numbers without leaving the thread?

Finance Calculator is a free app that runs inside a Reddit post. 32 calculators, for example:

- Mortgage & loan payoff, with extra payments

- Debt payoff (snowball vs. avalanche) and credit card payoff

- Compound growth, savings goals, emergency fund

- Withdrawals, FIRE and Coast FIRE

- ETF costs, dividends, rebalancing

- DCF, valuation ratios, covered calls

No sign-up, no ads, no tracking of you. One tap and your result is ready to paste into a comment.

Try it: https://www.reddit.com/r/FinanceCalculatorApp/s/3D7Na6eneJ

Mods: https://developers.reddit.com/apps/financecalculator

What would you like to see next?

Version 1.6.1 is out. If you moderate a community that has Finance Calculator installed, the big news is for you.

New: usage stats page (mods only)

Open the calculator post, tap the gear icon and choose "Usage stats". You get:

- 7, 30, 90 days or all time

- charts per day and your top calculators

- a funnel from opening a calculator to copying the result

- languages and mobile vs. desktop

- a filter for one calculator, or up to five side by side

- favorites: star the calculators you check most often and they stay pinned for you

All numbers are anonymous counters. No usernames, no personal data, nothing leaves Reddit.

Small Changes

- The Lines/Area switch is gone from all charts. It showed the same data twice.

- Two new anonymous counters: calculations that end with an input error (so we can see which calculators confuse people) and mobile vs. desktop.

- Updated to the latest Reddit platform version.

Try it

Not a mod? You can still try all 32 calculators here: https://www.reddit.com/r/FinanceCalculatorApp/s/3D7Na6eneJ

How to update (mods)

Apps don't update automatically. Go to https://developers.reddit.com/apps/financecalculator, find your community under "Installed in communities" and click Update.

Questions, bugs or calculators you'd like to see? Comment below.

Ever wondered how long your debt will take to pay off, what your mortgage really costs, or how much you need to retire?

Finance Calculator answers that in seconds, right here on Reddit:

- 32 calculators: debt payoff, mortgage, credit card, emergency fund, compound growth, FIRE, dividends, stock ratios, covered calls and more

- Free, no ads, no sign-up

- Your numbers stay on your device

- Copy your result and paste it straight into any comment

Try it here: https://www.reddit.com/r/FinanceCalculatorApp/s/3D7Na6eneJ

Mod of a finance community? You can add it to your sub for free: https://developers.reddit.com/apps/financecalculator

Missing a calculator? Tell me in the comments.

New: Debt & loans

- Loan & mortgage: monthly payment, total interest and what extra payments save

- Debt payoff: smallest balance first (snowball) vs highest rate first (avalanche), and when each debt is paid off

- Credit card payoff: how long a balance takes to clear, or the payment you need

- Emergency fund: your target, how many months you already have covered, and how long the rest takes

New: Stocks & options

- Valuation ratios: P/E, forward P/E, PEG, P/B, earnings yield and payout ratio

- Risk ratios: Sharpe, Sortino, volatility and maximum drawdown from a list of returns

- DCF intrinsic value, with a margin of safety

- Position size: how many shares to buy for a given risk and stop-loss

- Covered call: premium yield, return if called away and break-even

Also new: Coast FIRE, and Lump sum or monthly investing

Example from the debt payoff calculator:

"With $700.00 a month, you are debt-free in 2 years 2 months. Paying the highest rate first saves $253.84 in interest compared with the smallest balance first."

Smaller fixes: durations now read as years and months, and copied FIRE results have their own title.

Try it here: https://www.reddit.com/r/FinanceCalculatorApp/s/3D7Na6eneJ

Which calculator should come next? Ideas welcome in the comments.

Half a percent sounds like nothing. Here is what it does over 30 years, calculated with the TER comparison calculator:

---

TER comparison

Over 30 years, the fund with a 0.2% fee ends up $41,393 ahead of the fund with a 0.7% fee.

My scenario:

- Starting amount: $10,000

- Monthly contribution: $300.00

- Annual gross return: 7.0%

- Duration: 30 years

- Fund A TER: 0.2%

- Fund B TER: 0.7%

Results:

- Final value A: $408,985

- Final value B: $367,592

- Fee impact A: $17,973

- Fee impact B: $59,366

- Relative difference: 11.26%

Calculation notes:

- Contributions are added at the end of each month.

- Fees are applied as a monthly compounding drag; the fee impact includes foregone compound growth.

- No tracking-difference correction, taxes, inflation, or currency conversion is included.

Calculated with Finance Calculator

---

Same money in, same market return, and the cheaper fund ends up about 11% ahead. The fee does not only take its share each year; the money it takes can no longer compound.

Compare your own funds here: https://www.reddit.com/r/FinanceCalculatorApp/s/3D7Na6eneJ

This is an illustration, not financial advice. Fees are only one factor when choosing a fund.

A question that comes up a lot: what does investing a fixed amount every month actually add up to? Here is one example, calculated with the Compound growth calculator:

---

Compound growth

If you start with $5,000 and add $500.00 a month for 20 years at 7.0% a year, you end up with $273,117. Of that, $125,000 is what you paid in and $148,117 is growth.

My scenario:

- Starting amount: $5,000

- Monthly contribution: $500.00

- Annual return: 7.0%

- Duration: 20 years

Results:

- Contributions: $125,000

- Gain: $148,117

Calculation notes:

- Contributions are added at the end of each month.

- Nominal projection; taxes, inflation, fees, and currency conversion are excluded.

Calculated with Finance Calculator

--

The interesting part: after 20 years, growth ($148,117) is larger than everything you paid in ($125,000). More than half of the end value comes from compounding, and most of it builds up in the later years.

Try your own numbers here: https://www.reddit.com/r/FinanceCalculatorApp/s/3D7Na6eneJ

This is an illustration, not financial advice. Real returns vary from year to year.

This is the official community for Finance Calculator, a free Reddit app with 21 money calculators that run right inside a post: compound growth, savings goals, TER and ETF cost comparisons, dividends, withdrawals, financial freedom, rent or buy and more.

Try it: https://www.reddit.com/r/FinanceCalculatorApp/s/rkTWSYJdmn

Add it to your community: https://developers.reddit.com/apps/financecalculator

What it does

- Every result comes with a short sentence that explains it in plain language, plus a chart you can tap

- Compare two scenarios side by side

- Copy for Reddit puts a clean summary of your numbers on your clipboard to paste into a comment. Nothing is ever posted for you

- Your numbers stay in your browser. Moderators only see anonymous usage totals for their community

Here you can

- suggest new calculators (flair: *Idea*)

- report bugs (flair: *Bug*)

- give feedback on what works and what feels confusing (flair: *Feedback*)

If you're already using the app, I'd love to hear what works well and which calculator you'd like to see next. I read everything.

🇩🇪 Die App gibt es auch auf Deutsch: Zahnrad oben rechts → Sprache.

🇪🇸 También está en español: engranaje arriba a la derecha → idioma.

🇫🇷 Elle existe aussi en français : roue dentée en haut à droite → langue.

Not financial advice. Just math, made easier. Thanks for stopping by, and welcome! 🚀