HDConvert application icon HDConvert Engineering Units Conversion Calculator

HDConvert is a fast, fully customizable desktop unit converter built for HVAC and mechanical engineering professionals. It ships with a comprehensive library of engineering unit categories — covering the quantities most commonly encountered in building systems design — and lets you add, edit, or remove categories and individual units at any time using your own conversion equations.

HDConvert goes beyond a simple lookup table. Every conversion is driven by a two-step equation engine: each unit stores its own formula to convert to and from a common base unit. This means any unit in a category can be converted to any other unit in that category in a single operation, and new units can be added simply by supplying the appropriate formula — no programming required.

Conversion is fully bidirectional: type a value into either the input or the output field and the other updates instantly. This makes it easy to work backwards from a target value without manually inverting a formula.

KEY FEATURES

  1. Comprehensive built-in unit library — dozens of engineering categories covering temperature, pressure, flow rate, velocity, length, area, volume, mass, density, energy, power, heat transfer, and more; all stored in an editable database.
  2. Bidirectional conversion — enter a value in either the input or output field; the other field updates immediately, so you can work forward or backward through any conversion without doing anything extra.
  3. User-customizable categories — add new conversion categories for any quantity your work requires; enable or disable existing categories to keep the selector uncluttered.
  4. User-customizable units — add new units to any category by entering a plain-text equation that converts the unit to and from the category’s base unit; arithmetic operators, parentheses, and the built-in variable x are all supported.
  5. Equation-based conversion engine — conversions are computed from stored algebraic equations rather than fixed factor tables, so any unit relationship — linear, affine (temperature scales), or polynomial — can be represented accurately.
  6. Tab Manager — a dedicated editor for managing the full category and unit library: add, rename, or delete categories; add, edit, or remove individual units; set the base unit for each category; and toggle categories on or off without deleting them.
  7. Clipboard copy — exports the current input value, output value, and unit names as tab-delimited text for pasting into spreadsheets or project reports.
  8. Windows Calculator launch — opens the Windows Calculator directly from the toolbar for quick arithmetic without leaving the application.
HDConvert main conversion interface screenshot

HOW IT WORKS

Using HDConvert is straightforward:

  1. Select a conversion category from the drop-down list (for example, Pressure, Temperature, Flow Rate, or any category you have added).
  2. The two unit lists populate automatically with every unit in that category. Select the input unit from the left list and the output unit from the right list.
  3. Type a value into either the Input or Output field. The conversion result appears instantly in the opposite field.
  4. Switch units or categories at any time — both fields update immediately.

CUSTOMIZING THE UNIT LIBRARY

The Tab Manager (opened from the toolbar) gives full control over the conversion database:

  • Categories (Tabs) — each category corresponds to a physical quantity; you can add a category for any quantity your work requires, rename existing ones, toggle them on or off in the selector without deleting them, or delete a category and all of its units entirely.
  • Units — each category can hold any number of units; adding a unit requires only its display name and two plain-text equations: one that converts the unit’s value to the category’s base unit, and one that converts the base unit’s value back to this unit. For a simple scale factor (e.g., feet to inches) the equations are just x * 12 and x / 12. Affine scales such as temperature use an expression like (x - 32) * 5 / 9.
  • Base Unit — each category designates one unit as its base; all other units in the category store equations relative to it. Changing the base unit requires updating the equations for the other units accordingly.
View more app screenshots here.

System Requirements

  • Windows 10 or Windows 11
  • .NET 8 Runtime (included in installer)
  • 50 MB disk space

About Hands Down Software