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Rule of Thumb


The financial term “Rule of Thumb” is an informal guideline or principle that provides simplified advice regarding a particular subject, not intended to be strictly accurate or reliable for every situation. In finance, it often refers to simplified strategies for investment, saving, or budgeting. Some examples include the ’50/30/20 rule’ for budgeting or the ‘4% rule’ for retirement savings withdrawal.


The phonetic pronunciation of the phrase “Rule of Thumb” is: /ru:l ʌv θʌm/

Key Takeaways

Three Main Takeaways about Rule of Thumb

  1. The Rule of Thumb generally refers to a principle with broad application that is not intended to be strictly accurate or reliable for every situation. It’s often a simplified procedure that helps in making quick, live-time decisions.
  2. Rule of Thumb is used in many fields including engineering, business, and finance as a guideline or rule that is based on practical experience rather than theory. For instance, in finance, one may use a rule of thumb to decide how much to save each month.
  3. The origin of the term “Rule of thumb” is widely debated, but it generally is considered as referring to the use of one’s thumb as a rudimentary measurement tool. Despite its possible physically-based origin, it’s now used metaphorically to suggest an easily learned and remembered guideline or principle.


The Rule of Thumb, in the context of business and finance, is important due to its role in providing a quick, easy, and broad estimation strategy for making complex financial decisions and predictions. It simplifies complex data into understandable, applicable guidelines. For instance, it enables an individual or entity to loosely determine the feasibility of an investment, potential years required to double the investment through compound interest, or the sustainability of an enterprise’s debt level. However, while advantageous for its simplicity and speed, it is critical to remember that the Rule of Thumb is a general guideline rather than an exact calculation, and therefore may not always prove accurately reflective of specific situations.


The purpose of the ‘Rule of Thumb’ in finance and business is to simplify complex financial concepts, calculations, and guidelines into straightforward, general principles that are easy to follow. It can be applied in several areas including evaluating investments, setting financial goals, calculating retirement savings, budgeting, and much more. These rules help in quick decision-making, often suitable for a majority of people, and allow those without specialized financial knowledge to make sound financial decisions. However, they may not cater to individual circumstances or financial nuances, and as such, should be used as a starting point rather than a one-size-fits-all solution.The ‘Rule of Thumb’ serves as a helpful tool, providing a baseline for individuals or businesses to manage or assess their financial health, and steer their financial strategies. For example, in retirement saving, a popular rule of thumb is to save at least 15% of your income each year. In budgeting, the 50/30/20 rule suggests that 50% of your income should go to needs, 30% to wants, and 20% to savings. For investments, a common rule of thumb is the “Rule of 72,” which estimates how long it will take for an investment to double given a fixed annual rate of interest. These examples demonstrate how the ‘Rule of Thumb’ provides accessible and uncomplicated financial guidance to a wide array of individuals and businesses.


1. The 50/30/20 Rule: A popular budgeting rule of thumb in the world of personal finance is the 50/30/20 rule. It suggests allocating 50% of your income to essential expenses like rent and food, 30% towards lifestyle choices like social events or vacations, and 20% to savings or paying off debt. 2. The 100 Minus Age Rule: This is a common rule of thumb in the investment world which suggests that the percentage of stocks in your portfolio should be equivalent to 100 minus your age. So, if you’re 30, you should keep 70% of your portfolio in stocks and the rest in safer securities.3. Payback Period Rule: In business finance, a rule of thumb regarding investments or major purchases is that a payback period of three years or less is desirable. This rule helps businesses assess the risk of an investment by seeing how long it will take for them to recoup their initial investment.Remember, while these rules of thumb can be helpful starting points, individual circumstances can greatly impact the best approach. Always consider consulting with a professional for personalized advice.

Frequently Asked Questions(FAQ)

What is the Rule of Thumb in finance and business terms?

The Rule of Thumb refers to a basic principle or guideline that individuals can follow as a general advice. This doesn’t apply to every situation but is considered good and useful enough that it’s recommended most of the time. In finance and business, this concept can be applied in many situations like budgeting, investing, accounting, and other financial decisions.

Can you give an example of a Rule of Thumb in finance?

A popular Rule of Thumb in finance is the 50/30/20 rule for budgeting. According to this rule, you should allocate 50% of your income to needs, 30% to wants, and the remaining 20% to savings or paying off debts.

How precise is the Rule of Thumb?

A Rule of Thumb provides guideline but it is not absolute nor exact. It’s usually a good starting point, especially for those who are new to financial decision-making. However, it should be adjusted according to individual circumstances and needs.

Is the Rule of Thumb the same in every country?

While many Rules of Thumb hold relevancy broadly, some may vary depending on the economy, financial system, and cultural norms of a specific country. Therefore, it’s necessary to incorporate regional and personal context when applying these rules.

Can the Rule of Thumb be used in investment decisions?

Yes, the Rule of Thumb may be used in investment decisions. For instance, one common rule for investment is the 110 minus age rule. This suggests that you should subtract your age from 110 to decide what percentage of your portfolio should be allocated to stocks, with the remainder in less risky investments.

What are the limitations of using the Rule of Thumb in finance and business?

The Rule of Thumb serves as a general guideline and may not be applicable to all situations. Personal factors such as financial goals, risk tolerance, income, expenses, and economic conditions could significantly impact the effectiveness of these rules. Hence, it’s crucial to consider these rules as starting points and personalize them to your specific situation.

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