Valuing Your Labor With

Fermi Estimation

(Super-scientific guesses)

But Really

Interview Questions!

Also great for technology

Also great for technology

provide the basis for a discussion

Also great for technology

provide estimates for a project

provide the basis for a discussion

Also great for technology

provide estimates for a project

estimate the feasibility of an opportunity

provide the basis for a discussion

Also great for technology

provide estimates for a project

estimate the feasibility of an opportunity

determine if an answer that you have obtained makes sense

provide the basis for a discussion

Also great for careers

provide cost estimates for a project

estimate the return on investment of an opportunity

determine if an offer that you have obtained makes sense in relation to the company's budget and the project

provide the basis for a discussion about a raise

The Technique:

The Technique:

Identify the components of the answer

The Technique:

Divide the problem into small steps

Identify the components of the answer

The Technique:

Identify all the information you have

Divide the problem into small steps

Identify the components of the answer

The Technique:

Identify all the information you have

Determine what you have enough information for to factor into your problem

Divide the problem into small steps

Identify the components of the answer

The Technique:

Identify all the information you have

Determine what you have enough information for to factor into your problem

Divide the problem into small steps

Make an order-of-magnitude guess for what you don't have

Identify the components of the answer

The Technique:

Identify all the information you have

Determine what you have enough information for to factor into your problem

Divide the problem into small steps

Solve each step

Make an order-of-magnitude guess for what you don't have

Identify the components of the answer

The Technique:

Identify all the information you have

Determine what you have enough information for to factor into your problem

Divide the problem into small steps

Solve each step

Combine each step into an answer

Make an order-of-magnitude guess for what you don't have

Identify the components of the answer

The Technique:

Guessing

Rounding makes things easier to calculate- we only really care about orders of magnitude

The Technique:

Guessing

Rounding makes things easier to calculate- we only really care about orders of magnitude

Item    Exact Value    Suggested Value (for faster calculation)

    1 day    24 hours    25 hours

    1 mile    5280 feet    5000 feet

    1 yard    0.9144 meter    1 meter

    1 foot    30.48 cm    30 cm

    1 pound    453.6 g    500 g

    1 hour    3600 seconds    4000 seconds

Identify all the information you have

Identify all the information you have

How many kilometers are there in a light-year? 

(2 mins: put your answers in chat)

Identify all the information you have

How many kilometers are there in a light-year? 

How long is a light-year?

(2 mins: put your answers in chat)

Identify all the information you have

How many kilometers are there in a light-year? 

How long is a light-year?

c = 186,000 miles / second

(2 mins: put your answers in chat)

Identify all the information you have

How many heartbeats are there in a year for the entire world's population?

Divide and Conquer

How many heartbeats are there in a year for the entire world's population?

Divide and Conquer

How many heartbeats are there in a year for the entire world's population?

What smaller problems is this composed of?

Divide and Conquer

How many heartbeats are there in a year for the entire world's population?

What smaller problems is this composed of?

How fast does one person's heart beat?

Divide and Conquer

How many heartbeats are there in a year for the entire world's population?

What smaller problems is this composed of?

How fast does one person's heart beat?

How many heartbeats per year?

Identify all the information you have

For the average person, how many times will their heart beat during their lifetime?

What do we know?

What do we have to guess?

(2 mins: put your answers in chat)

Divide and Conquer

How many heartbeats are there in a year for the entire world's population?

What smaller problems is this composed of?

How fast does one person's heart beat?

How many people are there?

How many heartbeats per year?

Divide and Conquer

How many heartbeats are there in a year for the entire world's population?

Earth's population * Heartbeats per year

Divide and Conquer

How many heartbeats are there in a year for the entire world's population?

Earth's population * Heartbeats per year

2,400,000,000 heartbeats per year in the US

Career Examples

How much cloud spend does reducing server lag by 100ms save?

Assume all XHR queries currently take about ~ 1 second to process.

Divide and Conquer

Smaller Problems:

How many requests per hour do we need to serve?
How many servers do we need?
How much do servers cost?
 

Divide and Conquer

Smaller Problems:

How many requests per hour do we need to serve?
How many servers do we need?
How much do servers cost?
 

What would we need to guess about in an interview?

What don't we need to guess about when we're on the job?

Career Examples

How much cloud spend on our API servers does fixing one bug that causes an extra page refresh for each visitor save?

Assume all XHR queries currently take about ~ 1 second to process.

Career Example Homework

You're the principal engineer on a new feature that allows users who offer a hosting experience to also offer other services, for which your company gets a fee of 10% of the cost of service.

What information do you need to figure out the profit your company derives from this feature?

Copy of Fermi Estimation

By LizTheDeveloper

Copy of Fermi Estimation

  • 243