# 5-Step Process to Checking Engineering Calculations

Is checking engineering calculations important? Yes! Even the best of engineers make mistakes. Mistakes that could lead to failures and death.

So, by checking engineering calculations, you can prevent problems. This is especially important for design work that impacts the public.

I’m going to go over the 5-step process that I use with my engineering work. And that many others in all types of engineering use as well.

You can apply these steps if you’re the engineer doing the calculations or reviewing. In fact, you don’t even need to be an engineer. This is just a great way to check your work.

## Engineer’s responsibility to ensure public safety

As I’ve already once mentioned, an engineer needs to do the best job they can to ensure the safety of the public.

No different than a surgeon who cuts you open to safely operate on you.

This is best illustrated by a Swiss Federal Institute of Technology study done in Zurich. The study analyzes 800 cases of structural failures.

The failures led to the death of 504 people and tens of millions of dollars of damage.

Here are the reasons for the failures, with how often each happened.

Cause of engineering structural failuresPercentage rate of occurrence
Insufficient knowledge36%
Underestimation of influence16%
Ignorance, carelessness, negligence14%
Forgetfulness, error13%
Relying upon others without sufficient control9%
Objectively unknown situation7%
No clear definition of responsibilities1%
Other3%

Most of these things you can prevent through proper calculation checks. It’s one reason many engineers advocate for engineering licenses.

On that note, let’s go over the 5-step process to checking engineering calculations.

## STEP #1: Gather all your calculations together

Gather up all your completed calculations. Make sure the calculations show all your math steps.

Important Note:

Math steps: always show all your steps in your math work. Even for simple problems.

This way you and others can more easily figure out what you did. And why you did it. A year from now, everything will become foggy.

## STEP #2: Self-check your calculations

After you complete your calculations, wait a couple of days. Then review your own calculations yourself.

This will give you a fresh mind, to better check for mistakes. Most always you’ll catch something that you had missed in the first go around.

Plus, this will create better-checked calculations to pass on to your reviewer.

I always check my own work before I pass it along to anyone else. And most all the time I find something that’s wrong or that I can improve.

Also, it’s a good time to add notes to your calculations. Or add a missing calculation step.

It’s very much like writing. Your first draft always will have issues no matter how great of a writer you are.

You need to go through your writing many times until you have something presentable.

Important Note: set aside time for self-checking calculations in your design work. Nothing should ever go out the door without a round of checking.

## STEP #3: Hand your calculations over to a qualified reviewer

It’s important the person who reviews your work has equal or greater experience than you. Otherwise, it defeats the purpose of the review.

Pointers for the review:

• Explain your calculations to the reviewer. Tell them what you’re calculating. Also, if there’s anything unique about your calculations they should know about.
• Give the reviewer enough time to review your calculations.

## STEP #4: Backcheck the reviewer’s comments

After the reviewer has completed their review, go review their comments on your own. This way you’re not directly influenced by the reviewer.

Also, check if the comments make sense to you. You don’t need to agree with everything. Maybe they made a mistake.

So, write down anything you don’t agree with.

### Sit down with the reviewer after your self-review

Discuss the comments that you don’t agree with, with the reviewer. The goal is to come to an agreement over the accuracy of the calculations.

If you can’t come to an agreement, bring in a third party. Another set of eyes never hurts.

In the end, everyone needs to agree over all parts of the calculations made.

Important Note: after you complete the review, write down everything you learned. This way, you document the little details that you’ll soon forget.

You don’t want to waste future time trying to relearn things you just picked up. As I’m sure you’ll do similar calculations in the future.

### Your relationship with the reviewer

Build a mentor relationship with the people who review your work if they’re senior. This is a great way to learn from others.

But, don’t expect them to hold your hand to do the calculations for you. Rather, use the opportunity to soak in as much knowledge as you can.

Most importantly, don’t be afraid to ask “stupid” questions.

Important Note: prepare yourself before you go seek help. What I mean is:

• Do as much of the work as you can before you hand it off. Don’t take a blank piece of paper and expect someone to do your work for you.
• Research the parts you don’t understand. This way, you can better understand an explanation when you seek help.

## STEP #5: Submit your completed calculations

Submit your calculations to your client or boss. Then call it a day.

Afterward, sit down and document everything you may have missed. Any notes you had previously forgotten to write down.

Great engineers always take great notes to remember everything they’ve learned.

I always think I’ll remember something, because of how important it felt at the time I learned it. But only a couple of months later, I won’t remember anything about it.

In the end, the goal is to keep the public safe. Better notes today, lead to better future designs.

To drive the point home, here’s a list of large failures from simple mistakes. And engineers could’ve avoided these problems with a proper design check.

EventYearWhat happenedCause
The Hyatt Regency walkway collapse1981Suspended walkways on the second and fourth floors collapsed killing 114 peopleDoubling the load on the upper walkway connections without adding additional structural support
Gulf War patriot missile failure1991U.S. missile failed to intercept an Iraqi missile, thus killing 28 soldiersArithmetic programming error in calculating and measuring time
Explosion of the Ariane 5 rocket1996Exploded 40 seconds after liftoff, costing \$500 million dollarsSoftware error in the inertial reference system
Loss of Mars orbiter spacecraft1999Lost in space costing NASA \$125 million dollarsDue to wrong units being used; English versus Metric units
Tokyo Disneyland’s Space Mountain derailment2004 Roller coaster car derailed because of broken axleAxle broke because of conversion error from English to Metric units
New Orleans’ levee system2005New Orleans was flooded killing 1,833 peopleStrength of soil not properly estimated, and flawed data used on land elevation

## Tips with checking engineering calculations

Use these tips whether you’re preparing the calculations or doing the reviewing.

### #1 Learn math & engineering concepts

Whether you do the calculations or become a reviewer, understand the math concepts. This will allow you to understand the engineering theory.

You don’t want to check arithmetic alone.

When you understand a concept, you’ll quickly know if a calculation is wrong. For example, a calculation outputs the top speed of a Ford Mustang is 10,000 miles per hour.

Right off the bat, you’ll know something is wrong. A Mustang or any car for that matter can’t go that fast. It’s physically impossible.

### #2 Verify formulas

Check equations and not only math. Sometimes your arithmetic is right, but you used the wrong equation.

This actually happens a lot. Because the engineer didn’t understand the concept behind the work they were doing.

### #3 Equation inputs

Verify all the inputs. Sometimes you use the wrong input figures from the start.

So, even if you did everything else right, the calculation will still be wrong.

### #4 Proper documentation

So, do the following:

• Providing the formulas before you start your calculation
• List and define all the variables before your calculation
• Write what unknown variable you’re solving for

I’ve reviewed many calculations where I didn’t know what the engineer was calculating. So, take a couple of extra minutes and add notes to your calculations.

Always trade places in your mind with the reviewer when you’re doing the calculations. Then think, what would you like to see when reviewing a calculation you’ve never seen before?

### #5 Unitsof measurement

Add units to your values. This is one good way to know if you’re even using the right equation.

Also, it’s a great way to tell if your calculated values make sense.

Let’s go back to our Ford Mustang example. Imagine your equation outputs the top speed of a regular Ford Mustang is 160 meters per second. Instantly you’ll know something is off.

But, 160 miles per hour makes sense.

### #6 Significant figures

Be consistent with the number of digits in your values. This will help with the degree of accuracy in your calculations.

Normally in engineering though, lack of significant digits won’t lead to huge failures. This is because of the safety factors we build into everything.

### #7 Mistakes

Every engineer makes mistakes. It’s expected.

So, don’t rush your designs even with a deadline around the corner. Your client won’t thank you if you turn in your design a week early but it fails.

Even more, if you’re designing something new, it’s even more of a reason to have a peer review. I know some engineers find it time-consuming.

But as cliche as it sounds, better be safe than sorry.

As a reviewer, speak with the engineer who did the calculations. Ask questions to see what other calculations they had checked.

If any replies sound strange, dig into more parts of their design work. More than likely, you’ll find something else that they did wrong too.

### #9 Following an engineer’s math

Be careful as a reviewer not to blindly follow another engineer’s math. You can easily duplicate their mistakes by following their math.

So, don’t rush through your review.

### #10 Formatted design notes

Find a way to neatly add notes to your calculations. Then stick with this note format.

This makes reading all your calculations easier. For example, if your notes are always written in blue, your eyes will always know where to go.

This will greatly help the reviewer too. Just tell them all your calculation notes are written in blue.

### #11 Self-learning

To create the best calculations, you need to self learn the material. What I mean is, you need to learn the ins and outs of all the formulas you use. And the concepts.

I know in some companies checking engineering calculations is rare. And maybe impractical.

Older engineers sometimes go by feel as they’ve been designing for 40 plus years. For example, they know a given structure design can probably hold a given load.

Forget all about that though. Don’t become lazy. Especially if you want to stay out of trouble.

Build good habits, and you’ll sleep better at night.

## “Checking Engineering Calculations” wrap up

Checking engineering calculations is a critical part of engineering. It’s why we have such little failures in designs today. Even with how advanced designs have become.

After years of experience, you can visualize certain designs in your head. You’ll be able to spot mistakes quickly without proof of even a calculation.

But, if you do something wrong once and it works, you’ll make the same mistake a second time. Even if you did it right for years, you’ll one day run out of luck.

An earthquake can for example crumble your design that you had considered bulletproof.

So, don’t ever feel ashamed or rushed to get your calculations checked.

I bet engineers of NASA, Jet Propulsion Laboratory (JPL), and Lockheed Martin wish they’d done a proper review for the Mars orbiter.

JPL used the metric system, while Lockheed Martin used the English system. The mistake in units led to NASA losing its \$125 million Mars orbiter.

What do you think is the best way to check engineering calculations? How often do you check your calculations?

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