I finished reading The Long Tail over the weekend. The name of the book comes from the increasing importance of the sum of products and services that sell in small numbers. It makes the case that because there are so many of them, adding up these little sales actually makes them more valuable then the small number of products that sell in huge numbers, i.e. the biggest hit is the sum of the non-hits.

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One thing you notice when you watch a lot of golf on tv is that the same commercials are repeated over and over ad nauseum. This past week was no exception. I must have seen the ING Your Number commercial at least 10 times. Clearly their marketing tactic worked, because I did indeed go to their website.

The premise of the commercial is that everyone has a number that correlates to the amount they’ll need to have saved to retire when and how they want. In the ad, people are carrying around a physical number. By going to the website, you can calculate your number and then find a new financial professional in your area or email it to your existing one.

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Everyone loves a good rule of thumb. Knowing that the number of cricket chirps in 15 seconds plus 37 is the approximate temperature _[1] is great . I usually do the old 100 plus my age comparison when I get my blood pressure checked as well. These ballpark estimates are easy to remember and give a close enough approximation for many things in life. Unfortunately, there are often way too many variables for a rule of thumb to be of any real value for personal finances.

There are some financial rules that are valuable, but they tend to be the ones that are math based. An example would be “Double your hourly rate and add three zeros to get approximate yearly salary.” Of course, even such a rule makes the assumption that you work 40 hours per week. These “rules of thumb” are what I generally file under Quick Calculations. They are more mathematical approximations

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The Rule of 72 is well known: Divide 72 by a rate of return to get the number of years for your money to double. Example: at 4.5% return it will take 72/4.5= 16 years to double your money

Here are a few more quick calculations:

Cost Before Taxes
Multiply an item’s cost by 1.4 to figure out what you need to earn before taxes to afford it
Example: A $250 Nintendo Wii will require 250*1.4= $350 in pre-tax earnings

Hourly Rate to Yearly Salary
Double your hourly rate and add three zeros to get approximate yearly salary
Example: at $20/hour, you make about 20*2 = 40 –> $40,000 per year

Yearly Salary to Hourly Rate
Opposite of above: Remove three zeros from your yearly salary and cut in half to get an approximate hourly rate
Example: at $60,000 per year you make about 60,000 –> 60/2 = $30/hour

Current Spending Versus Nest Egg Worth
Add a zero to the cost
Example: Using $2,000 for a new computer today would have been worth 2,000 –> $20,000 in a retirement account 30 years from now.

Calculations assume a 40 hour work week, 8% investment return, and 28% tax bracket.

This post will be used to list favorite calculators, etc

Quick Calculations
Karl’s Mortgage Calculator
Baby’s First Year Cost Calculator
I Volatility Options Calculator
What Your Time is Worth Calculator
Price Comparisons Over the Phone