15 financial rules of thumb that answer Life's toughest money questions 

You are a busy person, living in a busy world.  This makes investing time into analyzing every financial detail of your life extremely difficult. Unfortunately, you literally can't afford not to, or it will cost you big time in the future.  That's what makes financial rules of thumb so powerful.  They give you guardrails for making better financial decisions in a quick and simple way.  

For a financial rule of thumb to be worthwhile, it should be easy to understand and even easier to remember. With that in mind,  I've compiled a list of the most memorable and impactful principals that smart folks have used for years to get a leg up on their money.  To help you find just what you need, when you need it, I've organized them by the types of problems they are useful for solving.

Bonus:  Download a printable cheat sheet that will show what financial rules of thumb to use and and when you should use them.

​How Much Do I Need for Retirement?

1. Retirement Savings: 25 x your annual income

This is a quick way to figure out how much money you'll need to retire.  The thought here is that with  25 times your annual income saved, at retirement you can withdraw 4%  annually.  That amount would be equivalent to your current income, and assuming a 7% average annual return, you wouldn't negatively impact your nest egg.  Check out the example below.

  • Annual Income: $50k
  • Retirement Savings Needed: 25 x $50k = $1.25M
  • 7% Annual Growth at Retirement: $87k
  • 4% Annual Withdraw at Retirement = $50k

2. Monthly Retirement Contribution: 15-25% your annual income

So once you know how much you need to have at retirement, you'll need to determine how much to save each month to get you there.  Since your income typically goes up over the years, this number can fluctuate up and down a little depending on how you are tracking towards your retirement goals.

For the example above, if you saved 20% of $50k for 30 years, assuming a 7% average annual growth, you'd have over $1M saved by retirement.  In that case, you may want to increase the % for a few years, or try to increase your income.

How Should I Allocate My Investments?

3. Subtract Your Age From 120: Determine your portfolio's optimal asset mix

As you get older, the stability of your investments become even more important because you don't have as much time for things to recover if the markets take a dip.  The best way to lessen your risk over time is to reduce the amount of stocks in your portfolio, and increase the amount of bonds.  

This rule is so valuable because it helps you figure out when and how much you should invest in stocks vs. bonds based on your age.  That's done by subtracting your age from 120.  The resulting number is the % of stocks you should have, with the rest going to bonds.

So let's say you are in your mid-30's:

  • 120 - 35 = 85
  • This means that 85% of your portfolio should be stocks, and 15% should be bonds. 

What’s My Net Worth?

4. How To Calculate Your Net Worth: Everything you own - everything you owe

Understanding your net worth is a great way to cut through all the noise of your investments and debts, and find out how much your finances are truly worth.  It's super simple to calculate as well!

  • First, you add up all your assets, which typically includes checking, saving, and investment accounts, as well as your home.  If you have other items that retain or increase their value, feel free to include them.  
  • Second, add up all your debt including your mortgage, credit cards, medical bills, personal loans, etc.  If you owe money, include it here.
  • Finally, subtract what you owe from what you own, and that will give you your net worth!

​Can I Retire Early?

5. Safe Withdrawal Rate (SWR): 3-4% Annually

Do you dream about retiring while you're still young? Then you need to know this number.  The safe withdrawal rate is how much you can "safely" withdrawal from your investment accounts without drawing down on your principal.  At that point you are effectively living off just a percentage of your portfolio's growth, which hypothetically means you never have to work again!

Example: If you have $1M in investments, assuming a safe withdraw rate of 3%, you could withdraw $30K every year without negatively impacting your portfolio.

6. Passive Income Ratio: Income From Salary vs. Passive Investments

Another thing to keep your eye on if early retirement sounds exciting, is how much money you make from your day job vs. how much you make from passive investments.  In this case, passive investments covers things like dividend paying stocks, rental properties, or "passive" side businesses like blogging or selling a product.  

"If you don't find a way to make money while you sleepyou will work until you die."                                 - Warren Buffet

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How Much Should I Put in an Emergency Fund?

7. Emergency Fund Ratio: Monthly Expenses X 6

How much you need in your emergency fund can be subject to a lot of debate.  What it really comes down to is your own comfort and risk tolerance.  I'm super risk adverse, so for me and my family, we go with 6 months of expenses.  There is nothing wrong with having less, though you'll want at least 3 months.

Example:  $6000 in monthly expenses = $36,000 in Emergency Fund

8. Resiliency Fund: ~$1K

Your resiliency fund is the first thing you save up money for when you're getting out of debt.  In the Dave Ramsey Baby Steps, this is Step 1, also called your "baby emergency fund".  The main difference between the Dave Ramsey version is that your resiliency fund is always a stand-alone account, and not part of your big emergency fund.  This is so you have some wiggle room for when something inevitably goes wrong with your budgeting, but it's only a short term problem (weeks not months).

Am I Saving Enough Money?

9. Savings Rate: How Much You Save / How Much You Made

Since saving for the future is such a important part of personal finances, it makes sense you need a quick way to see how you're doing.  This rule is expressed as what % of your monthly income are you putting away for the future, including retirement and other shorter term goals. Generally speaking, you should shoot for between a 15-25% savings rate.  A powerful best practice is to use a monthly budget to determine your spending before the month begins, and determine what you'll have left for savings.  You can then begin paying yourself first a portion of that amount with every paycheck.

Example: If you earn $4k a month, and save/invest $1k of it, your savings rate is 25%.

How Much Can I Spend on "XYZ" Every Month?

10. The "50-30-20" Budget

First coined by Elizabeth Warren, the 50-30-20 Budget gives you a great way to determine how much you be spending on "Needs" (50%),  "Wants" (30%) and "Savings" (20%).

Check out this great infographic from The Balance for a simple overview.

11. Spending by Category

In addition to the 50-30-20 Budget, you can get even more tactical in your budgeting by following some simple category-based guidelines.  This is particularly helpful if you are constructing a zero dollar budget.

  • Housing Expense: No more than 25% of your monthly take home or risk becoming house poor!
  • Utilities: Aim for 5%, and remember to turn off the lights we you're not using them.
  • Food: It's easy to overspend here, so try to save money shopping for groceries.  Aim for 10-20%
  • Transportation: I'm a huge fan of buying cars with cash, but if you do take out a loan make sure you aren't spending over 10-20% of your income here, including insurance, gas, and maintenance.
  • Clothing: 3-5% should cover most families since you don't buy clothes every day, and they really should last you.  
  • Medical: This is a tough one since it's often times unavoidable.  Do your best to keep it around 3%, but understand that this will fluctuate as needed.
  • Personal & Discretionary: I consider this fun money.  It can go towards whatever you want, but keep it around 5-10%.
  • Savings and Retirement: As I mentioned earlier, this should be around 15-25%.
  • Debt Payments: The more you work on paying down debt, the more cash flow you will have later since you'll have less payments.   Pay as much as you can here.

What’s My Monthly Cash Flow?

12. Cash Flow: Monthly Income - Monthly Outgo

This is another simple but powerful financial rule of thumb to know.  Being able to identify how much cash flow you have is useful because it tells you exactly how much money you have available to pay down debt, or invest for your future.  The higher your cash flow, the better off you are.   

  • If  your monthly income is $5K
  • And your monthly outgo (expenses) is $4K
  • Your monthly cash flow is $1K

Recommended Reading: If you're interested in learning more about getting out of debt, budgeting, and planning for retirement check out our complete guide to the basics of personal finance.

How Much House Can I Afford?

13. Mortgage Ratio: Limit Mortgage To 2.5X Your Income

This ratio is useful in determining how much money you could spend on a house, but keep in mind it's just one data point.  You also need to make sure that your monthly housing expense doesn't exceed 25% of your monthly income.  

Example: If you make $50k a year, a $125K home isn't out of the question, assuming the monthly payments are only 25% of your monthly income. 

14. Housing Expense as a % of Income: 25%

As mentioned above, a solid financial rule of thumb for housing cost is that it shouldn't exceed 25% of your monthly income.  Keep in mind, that is all in cost, i.e. principal, interest, property taxes, etc.  

How Much Term Life Insurance Do I Need?

15. Life Insurance Multiplier: 10X Your Annual Salary

As a husband and parent, ensuring  my family is always taken care of is a top priority for me.  That's why I believe parents should have term life insurance in place in case something happens.  But how much is enough?  The conventional wisdom is somewhere between 8-12x your salary.  I split the difference and go with 10x. 

Do I Have Too Much Debt?

BONUS RULE: Debt To Income Ratio : Monthly Debt Payments / Monthly Gross Income

Your Debt To Income Ratio (DTI) is a valuable number to have because it tells you what % of your gross income is going to the service of debt.  So if your gross monthly income is $5k, and your debt payments are $2k a month, your DTI ratio is 0.4, or 40%.  Another way to phrase it is for every dollar you bring home, 40% is going to service debt.  

There is no "ideal" DTI, though I'd recommend keeping it under 35% if possible.  Ultimately, as you pay off debt, and eventually your mortgage, it will slowly go down until it's 0%.

“You must gain control over your money or the lack of it will forever control you.” 
― Dave Ramsey

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Conclusion

Bonus:  Download a printable cheat sheet that will show what financial rules of thumb to use and and when you should use them.

Financial rules of thumb are a great tool in your analysis toolbox, but always keep in mind there are always exceptions to the rules.  They are also not a substitute for doing in-depth critical analysis for situations like buying a house or planning for retirement.  

Also keep in mind, they don't help you if you don't act upon what they are telling you.  Think of them like you would a speedometer or fuel gauge in the your car;  all they can do is provide you information, but it's up to you to decide to slow down or fill up the tank.  

What other financial rules of thumb have you found useful?  Share them in the comments below!

You are a busy person, living in a busy world. That's what makes financial rules of thumb so powerful. This post also contains a free downloadable cheat sheet! 
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About the Author

Hello, I'm Ryan. Besides writing about personal finance my other passions include spending as much time as I can with my amazing family, running around my neighborhood, and continuing to refine my skills as a product manager. You can also follow me on twitter @TMPF_Ryan.

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