Construction Calculator - Help & User Guide

1. Entering Values

Enter values using your keyboard or the on-screen keypad. The calculator accepts regular numbers, fractions, and values with units. It automatically converts between units and displays results in your chosen output unit.

Basic number entry

• 12, 3.5, -2.5

Negative Numbers

To enter a negative number, key in or type in the number and click the ± button.
Typing in a minus sign before the number is interpreted as a minus operation.

Input Formats

• Feet and Inches: Enter as 5' 6" or 5ft 6in
• Decimal Values: Enter as 5.5 or 10.75
• Fractions: Enter as 5/8 for fractional inches
• Mixed Format: Combine formats like 5' 6 1/2" or 5' 6.5" for 5 feet, 6 and a half inches

Feet–inch entry

Use the feet key ft (or the ft symbol ') and the inch key in (or inch symbol "). Separate feet and inches with a space, not a hyphen. The hyphen will be treated as a minus sign.

Examples: to input 6 feet 9 1/2 inches, press the buttons: 6 ,ft,9,in,1,/(frac),2.
From the keyboard, you can also type: 6' 9 1/2" or 6 ft 9 1/2 in.

Pasting is allowed: if you paste a value like 6'-8" from a drawing or note, the calculator will correctly interpret it as six feet eight inches. When typing, use a space instead of a dash.

You may still use a dash inside the inch portion, e.g. 6' 5-7/8" is interpreted as “six feet, five and seven-eighths inches”.

Other supported units

• Length: yd,ft, ', in, ", m, cm, mm
  • Examples: 3.2m, 250mm, 6' 4", 4ft 6in
• Area: append ^2 (keyboard) or use the x² button
  • Examples: 10ft^2, 12in^2, 2.5m^2
• Volume: append ^3 (keyboard) or use the x³ button
  • Examples: 8ft^3, 0.2m^3, 12in^3

Keypad vs. Keyboard

The on-screen keypad provides numbers, operators, unit buttons (′, ″, ft, in, m, cm, mm), functions (√, x², π), and mode buttons (Length, Area, Volume). You can work entirely by keyboard, entirely by clicking, or mix both.

2. How Units Work

• Length Mode: For linear measurements (default)
• Area Mode: For area calculations (square units)
• Volume Mode: For volume calculations (cubic units)

Mix units freely (e.g., 4' + 1200mm or 8ft × 2.4m).

Results display in your selected output unit.

Consistent Units

Unit operations need to be consistent.
For example: you can add lengths to lengths, areas to areas, and volumes to volumes.
You can also multiply lengths to areas to get volumes. Or divide volumes and areas by length.

You can multiply or divide numbers with units by a unitless number (e.g., a quantity or rate). The resulting unit will remain the same.
For example, 5ft × 3 results in 15ft.

3. The Stack (“Tape”)

Each number and operation appears on a running list, or stack, similar to an adding-machine tape.

• Add/Edit: Click any line to edit that value; all results update instantly.
• Delete: Use DEL to backspace characters or the line’s delete icon to remove a row.
• AC (All Clear): Clear all entries and stack.
• Clear Stack: Clear all entries and stack.
• Operators & functions: +, −, ×, ÷, √, x², π all work with units. Dimensionally consistent results are produced (e.g., length × length → area, etc.).

4. Shortcut Keys

When typing feet–inch values, use a space between feet and inches (e.g., 6' 6"). A hyphen (-) is a minus operator during typing. Pasting values like 6'-6" is accepted.

5. Changing Output Units

Change how results are displayed at any time (no re-entry required). Use the Units control or the shortcut U to cycle.

• Length: ft-in, inches, decimal feet, mm, cm, m
• Area: yd², ft², in², m², cm², mm² (add ^2 after the unit when typing)
• Volume: yd³,ft³, in³, m³, cm³, mm³ (add ^3 after the unit when typing)

6. Adding Machine — Similarities & Differences

Similarities

• Visible “tape” of entries (the stack)
• Easy review, edit, and re-total
• Familiar keys (AC, DEL, +, −, etc.)

What makes the Jabacus Construction Calculator better for construction

• Unit-aware math: feet/inches, metric, and conversions are built-in
• Fractions & mixed units: job-site styles like 6' 6 7/8" work naturally
• Multidimensional: multiply lengths to get areas; areas by length to get volumes
• Instant unit conversions: switch between ft-in, inches, decimal feet, or metric on the fly
• Live recompute: editing earlier lines updates all downstream results

7. Quick Examples

8. Tips & Troubleshooting

• If a ft-in entry seems to subtract, ensure you used a space between feet and inches (e.g., 6' 6").
• Typing a dash (-) between feet and inches is treated as minus; pasted values like 6'-6" are accepted.
• Fractions should use numerator/denominator (e.g., 7/8). Mixed numbers can use a space: 6 7/8".
• You can always enter just inches or just feet and switch the output units later.

9. Tools

The left sidebar includes three mini‑tools that work alongside the calculator. Open them by clicking the Conversion , Geometry, or Board feet buttons at the top left.

9.1 Conversion

Fast unit conversions across common construction and engineering quantities. You can type values with units (e.g., 3.5 m, 2' 6 3/4", 12 psf) and the tool will auto‑detect the quantity and units.

• Physical quantity: Length, Area, Volume, Force, Linear Load, Pressure, Density, Torque/Moment.
• Input: Enter a value and unit (or pick units in the dropdown). Feet–inches are supported (6' 4 1/2", 6-4 1/2", 6/12 for pitch style, etc.).
• Output: Choose a target unit—result updates live.
• Send to calculator: Click the → button to push the converted value to the calculator.

9.2 Geometry (Rise/Run/Slope/Diagonal)

Give any two values and the tool solves the other two. Great for roofs, ramps, and stair layouts.

• Fields: Slope, Rise, Run, Diagonal.
• Slope units: Pitch (rise‑in‑12), Ratio (e.g., 4:12), Percent, or Degrees.
• Length units: ft‑in, ft, in, m, cm, mm, yd.
• Input helpers: You can type feet‑inch values directly in any length field; the tool will detect and switch the unit selector for you.
• From the stack: Click the ← next to a stack line to send a linear value into the currently active Geometry field.
• Back to calculator: Use the → button to send any result back to the calculator.

9.3 Board Feet

Compute lumber volume per piece and totals.

• Inputs: Thickness, Width, Length, Quantity.
• Units: Thickness/Width in in, cm, mm; Length in ft, ft‑in, m, cm, mm, yd.
• Outputs: Board Feet (per piece) and Board Feet (total).

Accepted ft‑in formats (all tools)

• 6' 6 7/8", 6′‑6 7/8″, 6-6 7/8", 6'‑6‑7/8"
• 78.875" (decimal inches) or 6.65625 ft (decimal feet)

Formats like with a hypen like 6'-6" are accepted in the sidebar tool.