"70% energy savings" or "printing costs reduced by €50,000" – impressive figures! But you ask yourself: Can this really be true? With Fermi Estimates, you can quickly check such statements even without expert knowledge. Learn how to recognize bullshit figures in this article!
Additional materials with further examples of Fermi Estimates (German) →
What Is a Fermi Estimate?
A Fermi Estimate – often known as a Fermi Question – is a method you can use to make quick and rough estimates when you lack precise data.
The aim is to estimate the order of magnitude of a number without spending hours researching it. This technique was developed by physicist Enrico Fermi, who was known for solving complex problems with astonishing accuracy using simple assumptions.
Fermi Questions are a popular way of testing candidates for their quick-wittedness, creativity or logic skills, especially in job interviews. Examples include questions such as "How many piano tuners are there in Chicago?" or "How many tennis balls fit in a school bus?".
However, Fermi Estimates are not only popular as a playful quiz in job interviews. They also help you to debunk unrealistic claims in everyday life.
Why Fermi estimates are so useful
Whether at work, in meetings or during sales pitches – we constantly come across numbers that sound "too good to be true". But if you're not an expert on specific topics or don't have the right niche knowledge, it's difficult to verify these statements. This is exactly where Ferm estimates come into play!
With a few simple assumptions and calculations, you can find out whether a number is plausible – or complete nonsense.
Example 1: 70% Energy Savings with LED Lamps
Imagine someone claiming: "If we switch to LED lights, we will save 70% of our energy costs in the office."
Sounds impressive, doesn't it? But let's take a closer look – with two simple Fermi Questions:
- How much energy does lighting in the office consume anyway?
In addition to light, there are many other power guzzlers in the office: computers, heating, ventilation, printers, microwaves, etc. Light is unlikely to account for more than 20 % of total electricity consumption. - How much does an LED lamp save compared to conventional lights?
LEDs are known to be efficient. A generous estimate would be an 80 % saving in light consumption.
Now let's calculate:
Total saving = proportion of light consumption x saving through LED = 20% x 80% = 16%
Even with very generous assumptions, you only achieve a saving of 16% – and not the claimed 70%. More realistic would even be only around 7%.
Conclusion: This statement smells suspiciously like bullshit.
Example 2: Saving €50,000 in Printing Costs Through Digitization
Another claim: "If we digitize the administration, we will save €50,000 per year in printing costs."
Here too, the Fermi Estimate helps by approximating the real figure using rough assumptions and roughly estimating the relevant factors, for example as follows:
- Employees in the authority: approx. 100
- Pages per day per person: approx. 20
- Working days per year: approx. 230
- Costs per printed page: approx. 2 cents
Calculation:
100 employees x 20 pages x 230 days x €0.02 = €9,200
This is well below the claimed €50,000. Another clear case of exaggerated figures.
Error Compensation: Why Rough Estimates Are Often Surprisingly Accurate
An important advantage of Fermi Estimates is what is known as error compensation.
You will sometimes misjudge individual assumptions – sometimes too high, sometimes too low. However, with several calculation steps, these errors often balance each other out. This method is therefore also extremely helpful for more complex questions in order to at least correctly estimate the order of magnitude.
Conclusion: Recognizing Bullshit with Fermi Questions
The possible applications for Fermi estimates are almost unlimited, for example:
- Checking business case calculations
- Estimating project costs
- Questioning marketing promises
- Preparing for typical job interview questions
The good news is that you don't have to be an expert to debunk unrealistic figures.
With Fermi Estimates, you have a simple but powerful tool at your fingertips to critically scrutinize statements and avoid being fooled.
Have fun calculating and debunking!
Find more Shorts and learning content on our platform!
