Spotlight: Calculated Industries Gradematic 100
Quick Facts
Model: Gradematic 100
Company: Calculated Industries
Timeline: 1983
Type: Grades conversion, Four Function
Power: 2 LR44/AR76 batteries
Number of Functions: 576 (see source)
Calculated Industries has three sequels to the Gradematic 100: Gradematic 200, Gradematic 3000, and Gradematic 4000.
Get that Grade!
The Gradematic 100 has four main modes:
* Four Function Calculator
* Timer
* Numerical Grades
* Letter Grades
Four Function Calculator (Calculate Mode)
The four function calculator is the basic calculator with the four arithmetic functions (+, -, ×, and ÷), the percent function (%), and one memory register. The [ MRC ] key acts as both a memory recall and clear. However, there is no square root or change sign key.
From any other mode, we can enter the Calculate mode by pressing the equals key [ = ].
Timer Mode
The timer has the ability to count down from a set time or count up (stopwatch).
Count Down: [ TIMER ], enter minute and seconds, then press [ TIMER ] again. The Gradematic 100 does not beep when the timer runs out.
Count Up: With the display at 0 minutes and 0 seconds, press [ TIMER ] starts the stopwatch. Press [ TIMER ] again to stop the time. The stopwatch can only be stopped once.
Numerical Grades Mode
In the Numerical Grades mode, we can enter numerical grades for students depending on the total number of assignments and tests. The general process is this:
1. Press the [ NUMERICAL GRADES ] key.
2. Enter the maximum total score, which would get the student an A+ grade, then press [ STORE*HI ].
3. Enter the minimum total score of which a student to earn a D- grade, then press [ STORE*LO ].
4. To see the break down, press the [ BREAK POINT ] key repeatedly. When ready, press the [ CONTINUE ] key.
5. For each student, enter each grade, then press the plus button [ + ]. When finished, press the [ STUDENT AVERAGE ] key get the average and the grade.
6. (Optional) Repeat step 5 to enter additional students. Press the [ MRC ] key to get the Class Average.
Example: In a class of six assignments worth 100 points each (for a total of 600 points), find a students’ average on the grades: 88, 78, 85, 92, 93, 90. The minimum grade for a D- is 60% of the maximum (360 points).
[ NUMERICAL GRADES ]
Display: E Hi Sc. 600 [ STORE*HI ]
Display: E Lo Sc. 360 [ STORE*LO]
Display: b.P. Press [ BREAK POINT ]:
360 d-
380 d
400 d+
420 C-
440 C
460 C+
480 b-
500 b
520 b+
540 A-
560 A
580 A+ (press [ BREAK POINT ] to repeat the cycle)
[ CONTINUE ] Display: Su Sd Gr
88 [ + ] 78 [ + ] 85 [ + ] 92 [ + ] 93 [ + ] 90 [ + ] Display: 6 526 (total points: 526)
[ STUDENT AVERAGE ] 6 3.26 b+
Note: For some reason, the grade below D is labeled E.
Letter Grades Mode
The Letter Grades mode operates in a similar way to the Numerical Grades Mode. The Letter Grades Mode has specialty keys [ A+ ] through [ E ]. The student average and class averages works the same way.
Example: Find a students average consisting of the grades A-, B, C+, B+, A-, A.
[ LETTER GRADES ]
Display: Ent Gr. [ A- ] [ B ] [ C+ ] [ B+ ] [ A- ] [ A ] [ STUDENT AVERAGE ]
Display: 6 3.33 b+ (average 3.33 B+)
Two Scales
The GradeMatic 100 has two GPA scales: one where A is worth 4 GPA points, and A is worth 12 GPA points. This scales can be toggled with [ A=12 ] key, which can be pressed at any time.
Final Thoughts
If you get a Gradematic 100, make sure that a manual is included. I purchased one from a local thrift mart for a $1.00 but there was no instructions. That led me to purchase another Gradematic 100 on eBay.
Another fine specialized calculator that was once made by Calculated Industries.
Eddie
All original content copyright, © 2011-2025. Edward Shore. Unauthorized use and/or unauthorized distribution for commercial purposes without express and written permission from the author is strictly prohibited. This blog entry may be distributed for noncommercial purposes, provided that full credit is given to the author.
