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I am quite impressed and encouraged by the positive response I've received over the last ten days regarding my posts on the International System of Units (SI). I admit that I presented a lot of information; I hope I succeeded in presenting it in a simple - and more importantly - considerate manner.

The concept of "key conversion points" should be beneficial to many people. Personally, I kept a laminated copy of points in my pocket while I retrained my brain a few years ago. Additionally, I found it extremely helpful to make changes to SI (or both) wherever possible (e.g. HVAC thermostat, weather reports, websites, GPS, etc.). Finally, I prepared myself for the long haul of making the change.

There are certainly those who will roll their eyes or ridicule you for using SI, but know this.... You are the one who can travel internationally with ease; you are the one whose superiors will look to when you need to interface with a team overseas; you are "bilingual" in measurements.

Congratulations. Let us hope that soon those who use SI in the USA are not the exception, but the rule.

Index of Ultimate Metrication Day articles:

2010-10-10: The Ultimate Metrication Day - Recognizing the "Ultimate Metrication Day"
2010-10-11: Getting in the Metric Mind-set - Changing mental habits
2010-10-12: It's still cold whether °C or °F - Temperature measurements
2010-10-13: Covering all our bases - SI prefixes and their use
2010-10-14: Going the distance - Measures of length (meters, miles, feet, etc.)
2010-10-15: Mass makes the world go 'round - Calculating mass/weight (kilograms, pounds, etc.)
2010-10-16: Not loud, just spacious - Volume units (liters, gallons, fluid ounces, etc.)
2010-10-17: Conversation and display - How to fit SI units into daily use
2010-10-18: Diverting for a time - A short introductory presentation about "Decimal Time" (which has no official tie to the International System of Units)
2010-10-19: Compatibility and consistency - Presenting the importance of moving toward a Metric America

Compatibility and consistency

Since the "Ultimate Metrication Day", I've written a lot about HOW to adopt the International System of Units (SI). I think it's time I address the WHY....

In that initial post, I mentioned the fact that the United States of America is one of only three countries which has not adopted SI. I'll repeat what I said then, this fact does not bode well for the USA (nor Burma and Liberia). We are at significant risk of falling behind and out of touch with our global partners. To use a very crude and cruel metaphor, we are quickly becoming the creepy guy who is awkwardly without taste or the skills necessary for effective communication.

The United States of America is a leader in technological development, business incubation, and social innovation; how then can we lag so behind every other country in something as significant as measurement. We risk losing our lead and respect in every area I just listed; in fact, we already have damaged our reputation in some areas thanks to confusion with using US customary units.

In 1998, the US space agency NASA (a clear leader in space exploration) "lost" a Mars orbiter because every team, in every firm, used SI except one. One team made the mistake of using US customary units; this was the direct cause of mission failure at the cost of hundreds of millions of dollars. [JPL NASA]

There have been (and continue to be) cases where confusion over units has resulted in injury and death because medication was incorrectly administered in the wrong dose. (I'm not even going to cite a specific example because of the sheer number; simply Google "wrong dose medication" and see how many are due to the use of incorrect units.)

Some people have chosen to hold to US customary units for the sake of "tradition" or because "it's not worth the expense of changing". All things WILL change, even "tradition". Furthermore, the expense of making a change is becoming notably less relative to the expense of converting/communicating/coordinating the difference between "us" and "them".

Diverting for a time

Have you ever pondered the logic behind our base 6 counting system for time? Or been confused by trying to figure out how many minutes or seconds are in two hours? four hours? six? If you have, you're not alone. To put it bluntly, our system of tracking time is messed up. It's confusing, weird to explain, even unnatural.

It's not really "metric" in the official International System of Units (SI) way - as I've been blogging for the last week - but there is at least one alternative to our current system of tracking the passage of time: decimal time.

The system of Decimal Time divides a day into 10 hours; where 0 is "midnight", making 5 "noon". It's an extremely simple concept to explain. Think of each moment as ticking away a percentage of that day. Noon is halfway through the cycle of the day, so 50% or 5:00.

Furthermore, each hour is divided into 100 minutes (00 through 99); again this gives us an extension on that percentage concept. The seconds of those minutes are the same. Fun fact, a "decimal second" is just about the resting heart rate of the average human being; meaning, you could almost keep time using your heart.

I, personally, use decimal time wherever I can, but - due the risk of confusing those around me - it tends to only be in specific instances where only my eyes are reading the display.

I'd like to demonstrate how natural decimal time is through some very simple exercises. Ready? (I guarantee you already know this as if you learned it as a child.)

If the sun rises at 2:50 and sets at 7:50, what percentage of the day was it transiting the sky?

How many minutes have passed between 5:00 and 7:00? How many seconds?

It's currently 9:23. How many minutes until it's 0:00?

Some of those were pretty tough, but I would guess that you figured them out with a little thought. Here are the answers: 50%; 200 minutes, 20000 seconds; 77 minutes.

Again, this is not related directly to the International System of Units nor would it be something which would be a part of the adoption of SI, but decimal time does demonstrate the strength and natural feel of a base 10 system.

Conversation and display

As I've mentioned before, the tricky thing about the adoption of the International System of Units (SI) in the US is getting more people to readily use its units in their everyday lives. You can assist with this process by presenting SI in a natural and logical way. (Avoid talking about SI with arrogance, as that will most likely cause the listener to stop caring all-together.)

Conversation, in our modern age, can be had in at least two ways: verbally and textually. Presenting SI equivalents textually is relatively easy. For example, 5 km (approx. 3 mi); 20 C (approx. 70 F); etc. Using SI equivalents in verbal communication can be a little more complex; especially if you haven't already performed the conversion.

Here are some ways in which I've managed to sneak SI into my everyday communication....

"Could I get a 10 meter cable from you? .... That's about 32 feet."
(In the pause, I was able to convert to feet for the gentleman. It also allowed the "10 meter" statement to sink in and give the "32 feet" more relevance in relation.)

"I try to drink about 2 liters of water while on that 40 km ride. 2 liters is pretty decent; it's about a half gallon, but I really should be drinking more than that on a ride that's nearly 25 miles." (Basically, I just repeated the same information two different ways.)

"Wow! It is warm in here! It's got to be at least 25 Celsius.... What do you think? Is it about 80 in here?"

Try it out. I think you'll find that people readily accept your use of SI, if you provide the necessary context WITHOUT coming off as arrogant or pushy.

Not loud, just spacious

"Yesterday" I looked at mass; in a few places within that article I mention volume, so I'd like to proceed in that direction "today".

The official SI unit of volume is the cubic meter (m³), but the common unit accepted for use along side SI is the liter (1 L = 1 dm³; reference prefixes for assistance). I'm going to choose to focus on the liter when it comes to the comparison to US customary units of volume.

US customary units are horribly overrun with measures of volume (even more so than the complications in measures of length): gallons, fluid ounces, cups, tablespoons, teaspoons, etc.! I'm going to only deal with gallons and fluid ounces; I'll let you handle the process of getting to those from the others. (Maybe it'll be extra incentive to simplify with down to consistent measures.)

Key conversion points for Volume (gallons / liters):

1 gal ≈ 3.8 L
2 gal ≈ 7.5 L
* 4 gal ≈ 15 L
8 gal ≈ 30 L
16 gal ≈ 60 L

With this I wanted to show the approximate relationship between 4 gallons and 15 L. Multiples of four can be easy to calculate and, as I've mentioned before, multiples of 5 are natural; which makes this match up almost clean.

For example, if you were trying to estimate how many Liters were in 20 gallons.... 20 gal = 4 gal * 5 ≈ 15 L * 4 = 60 L. Obviously, the approximation takes us off a bit, but you can see how this gets us in the same conceptual neighborhood.

Key conversion points for volume (ounces / milliliters):

* 1 fl oz ≈ 30 mL
8 fl oz ≈ 237 mL
16 fl oz ≈ 473 mL
20 fl oz ≈ 591 mL

Unfortunately, the approximation of 1 fl oz to 30 mL will quickly get out-of-hand as you multiply it out; therefore, I've included common fl oz measurements to help get the L equivalents into your memory. Keep in mind that 100 mL = 10% of a liter.

Mass makes the world go 'round

Some people might consider metrication a massive undertaking, but it can actually be very easy to accomplish if people put their weight behind the effort. Let's address that effort literally....

The unit used to measure mass in the International System of Units (SI) is the kilogram. (Yes, you read that correct; the base unit is the kilogram, not the gram.) I find beauty in the use of kilograms by way of its (approximate) relation to volume, but that's another topic.

Before getting to my key conversion points for mass, I want to point out that SI is already in wide-spread use for mass (and volume) for drug prescription/purchase/use (both legal and illegal). So, for many, the conceptualization of mass (whether it's a milligram or a kilogram) has already been well established.

Mass Key Conversion Points (kilogram / pounds):

0.5 kg ≈ 1.1 lbs
* 1 kg ≈ 2.2 lbs
** 5 kg ≈ 11 lbs
10 kg ≈ 22 lbs
25 kg ≈ 55 lbs
50 kg ≈ 110 lbs
* 100 kg ≈ 220 lbs

If you can remember the 1 kg = 2.2 lbs rule, then you should have an easy time performing the rough multiplication to convert. For example, 11 kg = 10 kg + 1 kg = (2.2 lbs * 10) + 2.2 lbs = 22 lbs + 2.2 lbs = 24.2 lbs.
It may be even easier to rely on the 5 to 11 rule; as five is a very easy number to round to and 11 multiplies easily enough¹. For example, 500 kg = 5 kg * 100 = 11 lbs * 100 = (10 lbs * 100) + (1 lb * 100) = 1000 lbs + 100 lbs = 1100 lbs.

As far as reversing the conversion, just remember that 2 lbs is "a little less" than 1 kg and then you can adjust the conversion once you have an estimated kilogram value. For example, 300 lbs "is a little less than" 150 kg... 150 kg = 5 kg * 30 = 11 lbs * 30 = (10 lbs * 30) + (1 lb * 30) = 300 lbs + 30 lbs = 330 lbs.

¹ For you math whizzes: Yes, the multiplication of 11 can be made into one step, but I tried to make it easy to digest for the general populace by breaking it out into 10 and 1.

AUTHOR'S NOTE: I apologize for the three day delay in posting; I've had some difficulty accessing the internet during times which are appropriate for blogging. I plan to write and date the "missed" entries (this one included) as if they were written on time, for organizational purposes.

Going the distance

How far is it to the grocery store? What is the top speed of your favorite vehicle? How tall is the dinosaur chasing you?

We use units of distance/length everywhere; it's an essential dimension for other measures as well (e.g. speed = distance/time, area = length A * length B, etc.). Establishing a foundational understanding of SI distance units is paramount to a strong basis in Metrication as a whole.

In opposition to our efforts to see metric in everyday use is the fact that - when it comes to distance/length - Americans are unilaterally presented with US customary units. Some examples: the speed limit signs are given in miles/hr, our construction experts deal in feet and inches, we hike "14ers" (mountains approximately 14,000 ft in height), we watch American football players on the 100 yard field.

Whereas we see feet, inches, acres, miles, yards, and even the rare league; the SI measures of distance only have ONE...the meter. This is a distinct advantage over customary units.

As I presented in the post about temperature, using "key conversion points" is a helpful method. Here are some that I use, but I encourage you to find/create your own as well.

Distance Key Conversion Points (miles / kilometers)

* 100 mi ≈ 160 km
+ 88 mi ≈ 141 km
* 75 mi ≈ 120 km
* 62 mi ≈ 100 km
55 mi ≈ 88 km
*50 mi ≈ 80 km
40 mi ≈ 64 km
30 mi ≈ 48 km
*20 mi ≈ 32 km
*10 mi ≈ 16 km
*5 mi ≈ 8 km
3 mi ≈ 5 km
1 mi ≈ 1.61 km

Once again, I've placed asterisks next to the ones I think are nice to remember well. (I also placed a + next to the one that Marty and/or Doc Brown should watch for.)

Length Key Conversion Points (meters / feet)

*1000 m ≈ 3280 ft
*305 m ≈ 1000 ft
100 m ≈ 328 ft
*25 m ≈ 82 ft
10 m ≈ 32 ft
*5 m ≈ 16 ft
2.5 m ≈ 8 ft
2 m ≈ 6.6 ft
*1.5 m ≈ 5 ft
1 m ≈ 3 ft

Remembering the 1000 = 3280 rule sometimes makes other mental math easier. The 305 (roughly 300) to 1000 rule can be convenient in conversion; for example, "People enjoy hiking '14ers' in Colorado; peaks which are 14000 feet high or about... 4200 meters tall [ignoring the 5s and performing mental math... 300 x 10 = 3000, 300 x 4 = 1200, 3000 + 1200 = 4200].

Don't forget to use the prefixes where convenient!

Covering all our bases

Over the next few days, I intend to introduce you to some of the base units of the International System of Units (SI). Before I do, I'd like to spend some time on the prefix; a major component of SI units and a key advantage over other systems of measure.

A prefix is added to a "base unit" to indicate a multiple (or subdivision) of that unit. (We're already somewhat accustomed to this idea in computing.) The beauty of the prefix is that it represents a power of ten (e.g. 1, 10, 100, 1000, etc.).

(Some) Standard SI prefixes (Name [symbol] Factor = Number "cardinal/ordinal"):

micro- [μ] 10^-6 .000001 "millionth"
* milli- [m] 10^-3 .001 "thousandth"
* centi- [c] 10^-2 .01 "hundredth"
deci- [d] 10^-1 .1 "tenth"
10⁰ 1 "one"
deca- [da] 10¹ 10 "ten"
hecto- [h] 10² 100 "hundred"
* kilo- [k] 10³ 1 000 "thousand"
mega- [M] 10⁶ 1 000 000 "million"
giga- [G] 10⁹ 1 000 000 000 "billion"
tera- [T] 10¹² 1 000 000 000 "trillion"

You can find more information (and a better chart) in the SI prefix Wikipedia article.

Spend some time familiarizing yourself with the prefixes. I placed asterisks next to the ones I believe are the most common. Learn the relationships between the prefix and its base (e.g. 1000 units in a kilo-, 100 centi- in a unit, etc.). Since our number system is base 10, learning/counting multiples of ten comes naturally (literally, on our hands and feet).

It's still cold whether °C or °F

One of the most challenging aspects of adopting a new measurement system is relearning the "feel" or "look" of things and estimating their measure. In the case of temperature, many people are able to estimate based on a lifelong association of what the number on a thermometer feels like. For example, 4.5°C (40°F) is "cold" while 40°C (104°F) is "hot".

We first learn the arbitrary word association with the feeling when we are children. We feel the sensation, then we learn to verbalize that sensation as "hot" or "cold". Later we assign a personal range of numbers to that sensation/verbalization.

Your brain has already formed its association between temperature scale and sensation; so we need to establish an overlay using new numbers. I use a method I call "key conversion points" to help myself quickly estimate equivalent values without the use of mental math or a calculator.

Key Temperature Conversion Points (Celsius benchmarks):

50°C = 122°F
40°C = 104°F
* 37°C = 98.6°F (Normal human body temperature)
* 35°C = 95°F
25°C = 77°F
* 21°C = 70°F (Room temperature)
15°C = 59°F
* 10°C = 50°F
0°C = 32°F (Water freezes)
-15°C = 5°F

Key Temperature Conversion Points (Fahrenheit benchmarks):

* 95°F = 35°C
80°F = 26.67°C
70°F = 21°C (Room temperature)
60°F = 15.5°C
* 50°F = 10°C
32°F = 0°C (Water freezes)
23°F = -5°C
* -4°F = -20°C
* -40°F = -40°C

Memorizing some (or all) of these conversion points will help you start estimating right away. (I put asterisks next to my favorites.) Eventually, the SI numbers will start to have the same impact as the customary unit values; you'll still think "cold" whether the weather is given in Celsius or Fahrenheit.

Getting in the Metric Mind-set

Americans have used customary units for centuries (though, officially, SI was made the basis for our units in 1893). We are habitually familiar with a certain system. The point is, we need to retrain our brains into a different way of thinking about measurements before we can fully adapt to or even adopt a new system; some people may find this more difficult than others.

The first step is to consciously accept "the Metric mind-set"; find a reason to value the use of SI measurements (e.g. base 10 counting, international communication/cooperation, etc.) [further reading: Metrication in the United States - Wikipedia]

Once you've acknowledged some value in the use of the metric system, I recommend observing where SI units are already used....

- Passing your local bank, try to remember the Celsius temperature display and how it feels.
- Pick up that large soft drink bottle at the grocery store and remind yourself, "Wow. This is a 2 LITERS."
- Look closely at the label on a gallon of milk.... How many milliliters does it contain? How many liters is that?
- Convert the distance of your commute from feet and miles into meters and kilometers. (Even if it's just 2 or 3 meters from the bed to the desk.)

These small thoughts and/or conversions will help you see how the things around you "measure up" to the International System of Units.

Tomorrow, I'll begin sharing some ways you can remember "key conversion points" to help you estimate equivalents in your head on-the-fly.

The Ultimate Metrication Day

As I have sometimes recognized in the past, October 10th is "Metric Day". This year is especially unique because it is October 10th of 2010 (10-10-10); making it a sort of "ultimate" day for encouraging metrication.

There are only three nations in the world which have not officially adopted the International System of Units (aka Metric System) as their primary or sole system of measurement: Burma, Liberia, and the United States. This is not a good thing for the United States; as we speed toward a lifestyle of inter-connectivity and international communication, it will become essential that the USA adapt or risk falling behind its global partners.

When recognizing "Metric Day" in the past, I've made an effort to spread the knowledge and usage of the International System of Units (SI). This year, in recognition of what I'll call the "Ultimate Metrication Day", I am going to up the ante....
Over the next 10 days (beginning on the 11th and going until the 20th), I will share a tip or technique about using SI in everyday life and make the conversion seem that much less daunting.