Documentation hub
HVAC resources, methodology and calculator guides
Guides, methodology notes and direct links to every HVAC Toolkit calculator: heat load, duct sizing, static pressure, VRF piping, refrigerant PT charts, acoustics and CAD drawing. Every tool works in both imperial and metric (SI) units, and every result is meant to be reviewed by a qualified engineer before it is issued.
Load & selection
Start every project by establishing the design load, then size terminals and emitters against it.
Manual-J style room-by-room cooling and heating load with climate, insulation and internal gains.
Open toolPick diffuser or grille type, quantity and neck size from airflow, throw and noise targets.
Open toolEN 442 output correction for the real mean water-to-room temperature difference.
Open toolAir distribution
Size ductwork on friction rate or velocity, then verify the fan can deliver the system total.
Darcy-Weisbach friction loss with ASHRAE circular-equivalent round and rectangular sizes.
Open toolAdd duct runs, fittings and components, then compare total ESP against the fan rating.
Open toolSMACNA gauge selection, sheet metal weight and leakage allowance for take-offs.
Open toolDrawing & site measurement
Lay out runs on a plan grid, review them in 3D, and capture real site dimensions from your phone.
CAD-style drawing with ortho lock, snapping, numeric dimensions, 3D view and DXF/SVG export.
Open toolMeasure walls, openings and areas with the camera, with calibration quality and session logs.
Open toolOctave-band 63 Hz to 8 kHz analysis of duct-borne noise with NC/room level results.
Open toolRefrigeration & service
Field references for commissioning, diagnosis and refrigerant piping.
Saturation pressure and temperature for R-410A, R-32, R-134a and more.
Open toolConvert gauge readings into superheat and subcooling with charge guidance.
Open toolLiquid and gas line sizes with height and equivalent-length limit checks.
Open toolASHRAE and SMACNA anchored guidance on sizing decisions and design review.
Open toolAirflow, pressure, power, temperature and length between imperial and SI.
Open toolReference reading
Engineering standards & methodology
Exactly which equations, tables and standards sit behind every calculator, plus scope limitations.
Plans & pricing
What the free tier covers, the 7-day trial, and what Pro and Team unlock.
Terms of service
How MJTOOLS licenses the toolkit and the responsibilities of the reviewing engineer.
Privacy policy
What project data is stored, where it lives, and how to remove it.