BoardCalc 3.0 User's Manual

1-Mar-2016    rev 3.0.14

BoardCalc 3.0 is an Android® OS application, a general-purpose calculator useful for working with wood.  BoardCalc ‘thinks’ in fractions, feet and inches, yards, board feet, or metric. It does conversions between metric and imperial units, decimal and fractions, board feet and areas/volumes. BoardCalc makes it a little more comfortable to subtract 5 5/8” from 1’ 3 3/32” or add 5mm to 7/8”.

The strength of this calculator is that it works in fractions or decimal with equal ease, works with dimensions in inches, feet, yards, cm, mm meters, or board feet, converts between units of measure or fraction / decimal, can round bizarre fractions to more sensible values, and calculates board feet from two dimensions, three dimensions, surface area or volume.
More info is available on the web at:



  1. Input and calculations
  2. Conversions
  3. Calculating Board Feet
  4. Rounding
  5. Memory registers
  6. Things to know
  7. Preferences (settings)
  8. Trial period
  9. Requirements

1) Input and calculations
Like most of the calculators you have used to do simple math, this is an algebraic input calculator (as opposed to RPN, Reverse Polish Notation). You enter the first value, then the math operation (such as '+'), the second value, and then '='. Each value in the calculation can be a plain number, length, area or volume. The only requirement is that the operation and the values given be possible: dividing a length by an area, for example, can't be done. If one value in an addition or subtraction has units and the other does not, both are assumed to have the same units: 5 + 5cm = 10cm. For multiplication or division, what you see is what you get, in order to correctly keep track of whether the result is an area, length or volume. 5 x 5cm is 25cm, while 5cm x 5cm is 25 sq cm.

Many are the ways to enter values in BoardCalc:
Fractions use the (sp) (space) and / (fraction) buttons. For example, to enter two and a half, the buttons  2  (sp)  1  /  2 are pressed.

Dimensions can be entered in feet/inches/fraction. If a value includes two whole numbers, it isn't necessary to include the units - the calculator knows that  2  (sp)  2  can only be feet and inches. A fraction on the end of two whole numbers works the same way (no units required). The following are all legal, and all represent the same value:
2'  2  1/2"       2  2  1/2"       2  2  1/2       2'  2  1/2      26 1/2"

Units: m = meters, cm = centimeters, mm = millimeters, yd = yards, ft = feet, and In = inches. If the screen is set to Small in Screen Size, only three of these will be visible at a time, below a button marked "i/m". This stands for "imperial/metric" (or inches/meters if you prefer). Pressing this button will swap the three buttons below it to m/cm/mm or yd/ft/In.

Multiple dimensions can be entered for a single calculation using the 'by' button. This can be useful to calculate area, volume or board feet.
3" by 8' BdFt              gives 2.00 bd ft
3" by 8' by 2 BdFt ]    gives 4.00 bd ft
1 by 2 by 3 =              gives 6
1 by 2 by 3 BdFt        gives 0.04 bd ft
1' by 2" by 3cm =       gives 21 44/127 cu in
2) Conversions
Converting a value to different units of measure is just a matter of entering the number, the original units, and the new units. If you already have a result of a calculation that has units, just press the new units. To convert from fraction to decimal or vice versa, either press the / (fraction) button, or press the same units again (pressing the 'in' button will flip between decimal inches and fractional inches, for example):
5 cm in                     gives 1.97"     (converted 5 cm to inches)
in (again)                 gives 1 123/127"   (converted decimal inches to fractional inches)
11' 7 3/4" '               gives 11.65'      (converted feet/inches/fraction to decimal feet)
in                              gives 139.75"    (converted decimal feet to decimal inches)
An area in any units can also be converted to BdFt, even though BdFt is a volume. The third dimension is assumed to be 1" (4/4).

3) Calculating Board Feet
A board foot is a measure of volume. If only two dimensions are entered, the third is assumed to be 4/4 when the BdFt button is pressed, since this is the most commonly used lumber.. A surface area is converted to board feet the same way, by assuming a thickness of 4/4. Either the by button or the x (multiply) button can be used between values when calculating board feet. Any number entered without units is assumed to be inches.
12" by 8' BdFt            gives 8.00 bd ft
12 by 8' by 1 BdFt     gives 8.00 bd ft
12 x 8' BdFt                gives 8.00 bd ft
3cm by 1m BdFt        gives 0.32 bd ft
8" by 8' by 1" =           gives 768 cu in
BdFt                            gives 5.33 bd ft
BdFt                            gives 5 1/3 bd ft

4) Rounding
A value like 1 123/127" is difficult to find on a ruler. You can round this value to something more sensible by touching anywhere in the display area where the value lives, and scrolling (moving) your finger left or right to change the rounding. Scrolling left will round to smaller and smaller fractions until 64ths are reached. Moving right will round to larger fractions up to 1/2. Scrolling all the way to the right will turn rounding off so that the exact fraction is displayed. A fraction can be rounded to the nearest 1/2, 1/4th, 1/8th, 1/16th, 1/32nd or 1/64th. This selector only affects how the value is shown, the exact value is always preserved.  If the displayed value is rounded, a '~' will show up in front of it to warn you, and the rounding value (such as 1/64th) will show at the lower left side of the display. There will be no '~' or rounding value if the value shown is exact, even if rounding is turned on.

The original fraction is not changed when it is rounded, only the display of the value is affected. If rounding is turned off again, the exact original value will be displayed again. All math will come out correctly, regardless of rounding, but results can look odd. For example, if you enter 3/16, and round to the nearest half, the result is ~0. Now press MS, '+' and MR, the display will show ~0 + ~0. The value 3/16 rounded to the nearest half is 0, which is shown twice in the display. Now pressing '=' will add 3/16 to 3/16 to give ~1/2. In recent calculations, the last calculation shows ~0 + ~0 = ~1/2, which is a nice trick if you can work it financially. Any time you see the '~', remember that the value is rounded.

Note that rounding does not force the fraction into the rounding chosen - fractions are always reduced as far as possible. If 1/2 is rounded to the nearest 1/64th, it will still show up as 1/2 (not 32/64, and no '~' is shown because the value is exact). And if 123/127 is rounded to the nearest 1/64th, it will show ~31/32.

5) Memory registers
There are ten memory registers, of which register 0 is special. The memory keys (MR, MS, M+, MC) in the calculator use register 0. A normal press on MS saves the current result to register 0. MR recalls the value from register 0 into the current calculation. M+ adds the current result to whatever is already in register 0. MC clears register 0. When a value is saved in memory register 0, an 'M' will show up in the left side of the calculator display. If you only use  these keys and don't need to save any other values, you need never look at the memory register page.

On the other hand, if you have calculations, measurements or values that you would like to refer to later on, there are nine more registers that you can use to save them. There are two ways to put a value in them: a long press on MS will bring up the memory register page. Pressing any of the ten lines will save the current result in that register and flip back to the calculator page. You can also fling across any screen or use the menu to change to the memory page. A long press on any of the ten lines will bring up a menu from which you can Save, Recall or Lock the memory register. Save will put the current result in the memory line (and stay on the memory page).

Recall works the same way: a value can be recalled from any memory register by a long press on the MR key and selecting a line, or by a long press on any line in the memory page and selecting Recall. When you recall a value from a memory register, BoardCalc will switch from the memory register page to the calculator page whe

Lock is useful if there are values in memory registers that you wish to protect from being accidentally replaced. A long press on the line and selecting Lock for the memory register will prevent any new value from being stored there. A locked value can still be recalled, and can be unlocked any time.

If a calculation is not yet complete, pressing MS or M+ will complete it and save/add the result to memory. For example, pressing 2 + 3 MS will show 5 in the calculator display and store 5 in memory register 0. The rounding and units of the calculator value will be saved in the memory value. Again, the accuracy of the value is not affected, only how it is displayed. But the same number rounded to two different bases can be saved in two memory registers, and will look different, even though they are exactly the same value and will give exactly the same results in any calculation.

The memory keeps track of units just as the calculator does. If you use M+ to add 5" to a value of 3 (no units) already in memory, the memory result becomes 8". Any math operation that won't work in the calculator will also fail for M+: trying to add a length to a volume will beep and do nothing.

If the calculator beeps when M+ is pressed, the operation is illegal and nothing was done. This is probably because the values are a mix of length, volume or area. Adding an area to a volume or length does not make sense. M+ with different units (mm/cm/m/in/ft) will always work as long as both values are length, both are area or both are volume. A value with no units can be added to anything. It will be given the units of the other value.

6) Things to know
i) Chain calculations
You can do a chain of operations without pressing the '=' button. Each time a new operation is pressed, the previous operation is calculated and the result is used as the first number for the new operation. For example, if you press 1 + 2 x 3 =, the result is 9. 1 + 2 becomes 3 when the 'x' is pressed. Then 3 x 3 = 9.

ii) Board Feet and the NHLA method
BoardCalc figures board feet by treating board feet as a volume: 144 cubic inches equals 1 board foot. It does not make corrections for thickness less than an inch or round thickness to the nearest 1/4. In fact, it does not do any rounding at all in the calculations. The answer calculated is therefore not necessarily what you would get using the NHLA method to calculate board feet, especially for multiple boards where you tally a surface measure first, rounding up one time and down the next. It was done this way so that you can always see what you get, with no hidden rounding to surprise you. If you need to use the NHLA method to calculate board feet, it is up to you to do the rounding. There are many discussions (and arguments) available about this topic on the web and elsewhere.

iii) It beeps at me
Sometimes the machine is smarter than we are. If BoardCalc beeps, it couldn't do what you asked it to. This usually means that the dimension of the result is impossible. Multiplying an area by an area, or adding a volume to a length, for example, will get you a beep, because these don't make sense.

If converting units for an area or volume, you don't need to press sq or cu, and you will be beeped if you do. All that is required is inches, feet, etc. BoardCalc already 'knows' that it is an area or volume.

iv) Overflow & Overrun
If numbers become too large internally, they can cause an overflow, which means that BoardCalc does not have enough room in a single number to hold the value or complete a calculation. If this happens, OVERFLOW is displayed. Too see this, enter 8888888888 (ten '8's) and press '='.

Internal to the calculator, all values are stored in inches. Because of this, it is possible for a large value to be valid in inches, but too large to convert to cm or mm. If this happens, the display will show Display Overrun. The value is still valid, but can't be shown in these units. To see this, enter 888888888" ( nine 8's and inches) and then convert to cm (press cm).

v) Accuracy
BoardCalc stores all values as fractions. This means that values entered as a fraction will always be exact, as opposed to most calculators that store values as a decimal mantissa with a power. 1/3 is really 1/3 in BoardCalc, rather than .333333333.... with some vanishingly small error. In practical terms, this just means that if rounding is not turned on, the fraction displayed is the exact value and not an approximation.

The accuracy of a value does not change when you round it. The displayed value is all that changes. This works the same way that decimal places do on this or any other calculator. You can display any number of decimal places you like, the value underneath is never affected. This can, however, lead to some oddness in displayed values (see History below).

Decimal values and math are accurate to about 8 significant digits. This is much less than most scientific calculators, and was done to keep BoardCalc small and agile. This level of accuracy would not be adequate if calculating orbital parameters for a satellite shot to Jupiter. But for an 8-foot board, an error of 1 in the 8th significant digit amounts to .0244 microns. For comparison, a bacterium is about 100 times larger (2 microns), and the thickness of a sheet of paper is roughly 5000 times larger (100 microns). So .0244 microns should be accurate enough for most woodworking. To see this, enter 200 cu m, and press m again to convert to a fraction. The metric value is converted to inches internally, which introduces an error that is cubed because this is a volume. The total error ends up being 1/10709948.

vi) Recent Calculations History
Every time the general-purpose calculator completes a calculation, it stores a line of text to the recent calculations history. The text contains the parts of the calculation and the result, as they appeared in the calculator display. The entire calculation appears in the same line, as in:
11" by 11" by 11" = 1331 cu in
2 + 3 = 5

If enabled in preferences (default) the list is saved when BoardCalc is exited. The list length is one page at the smallest text size (12). The most recent calculation is added below the other lines in the list. If the list is full, all the other lines are bumped up one line and the top line is thrown off. The list can be displayed in a number of text sizes, which can be selected from a context menu (long press) or in BoardCalc's settings. Changing the text size does not change the length of the list, only how much of it is displayed right now.

After a few sessions, the recent calculations list will fill up and stay full, putting new calculations at the bottom. If you would like to see only what you have done lately, the entire list can be deleted. Bring up the context menu of the history page (long press) and press Clear History at the bottom to delete the entire list.

vii) Percent
Adding or subtracting a percentage uses the units of measure of the other value. 20% + 10" is the same as 10" + 20% (12"). Adding percentages might not do what you expect. For addition or subtraction with two percentages, the first number has units of measure which happen to be percent, and the second value is used to do percentage math. If you enter 60% + 50%, BoardCalc adds 50% of the first thing (60%) back into it. 50% of 60% is 30%, so 60% + 50% = 90%.

For multiplication and division, percent values are simple, and never act like they have units of measure. 50% is just another way to say .50 or 1/2.

viii) Small screens, and the i/m button
On small devices, used in landscape mode, there isn't enough room to fit all the buttons into. You might notice that half the unit of measure buttons are missing, and an extra button labeled i/m has appeared. This i/m button swaps the units buttons between metric and imperial units. Either mm, cm and m are showing, or in, ft and yd are showing. Press i/m to switch to the other set.

ix) Fraction reduction
If a number is displayed as a fraction, it is reduced as far as possible. It isn't very useful to see a number like 8/16 in the display. There are, however, limits. To reduce a fraction, it is divided by a series of prime numbers. To keep calculation times reasonable, the primes only go up through 127. So any number that has factors up through 127 will reduce properly but anything with larger factors will not reduce completely. For example, if you enter 233/466, it will not reduce to 1/2.

7) Preferences (settings)
Preferences (settings) can only be reached from the menu.

a) Audible
Sets the level of audible feedback that sounds when a button is pressed. Choices range from none to 100% (full volume)

b) Haptic
Sets the level of haptic (tactile) feedback when a button is pressed.  Choices: none, low, medium, high. What each setting does may vary from one device to another, and some devices may not support haptic feedback at all.

c) Save history
Determines whether the history list will be preserved. Options are Save or Don't Save. If you choose Don't Save, the history  will disappear any time you leave the program, bring up settings, view the help, or rotate your device between portrait and landscape.

d) Rotation
Controls the orientation of the display. If Enabled, rotating your device will also change the calculator display.  Selecting Portrait will always take the long direction of the screen as vertical, regardless of any orientation sensor. Landscape will always take the long edge of the screen as horizontal.

e) Screen size
Android devices come in a plethora of shapes and sizes. On the smallest screens, the buttons in a normal layout can become so small that it is difficult to press the correct one, but there are acres of room to spare on a tablet. Screen size of Auto will use measurements from the device to pick the best fit. You can force the display to Small (intended for 3" screens), Normal (longer aspect screens), Tab 5 or Tablet. Small and Normal screens adjust to fill the screen, whatever size it is. The Small layout has had a row's worth of buttons removed: the remaining buttons will be larger (and easier to press accurately on small screens). Any device smaller than a 5" tablet will come up in Normal layout in Auto. If the buttons are too small, you can force them to be larger by choosing Small screen size in settings. For Tablet and Tab 5 settings,  the button sizes are fixed and the display puts all three pages (memory, calculator and history) up at once. Note that if you force the screen size to tablet on a small device, you may only see the memory registers, and appear to be stuck on that screen; since tablets show all three pages at once, switching between pages is disabled.

f) Screen timeout
Your android device has a setting for shutting off after being idle for a selected amount of time. Screen: Timeout will follow that setting and shut down. Screen: Keep on will ignore the setting and the screen will stay on as long as BoardCalc is showing.

g) History text size
The list of recent calculations can be shown in different sizes. Smaller fonts are harder to read but show more on the page. Readability and size vary from one device to another, so the choices range from 12 to 20.  The size selected has no affect on how much history is kept or stored, it only affects how much is displayed. This text size can also be set from the History page context menu (long press).

h) Help text size
The help text can be shown in different sizes. Smaller fonts are harder to read but show more on the page. Choices range from 12 to 20. This text size can also be set from the Help page context menu (long press).

i) Number format
Set this to the format you usually work in, either fraction or decimal. Any whole number you enter (with no fraction or decimal point) will take this format. Any math done with the number will then keep the default format. For example, with the default of Fraction, entering 2 + 1/2 = will yield 2 1/2. If the number format is changed to decimal, entering 2 + 1/2 = will yield 2.5 in the display: the '2' is taken as a decimal value, since it is ambiguous (not specifically either a fraction or decimal value). The '1/2' added to it does not change it's display format, it remains a decimal value.

8) Trial period
You can try this software out for 60 minutes after downloading. During the trial, everything  will be visible and fully functional. After the hour expires, everything will still be visible, but no button presses will be allowed.

9) Requirements for BoardCalc 3.0