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Quick MEP field reference — in your pocket.
Everyday
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Unit Converter
Temp, pressure, flow, power & more
📐
Rules of Thumb
Quick load & airflow estimates
💨
Velocity / CFM
Airflow, area & velocity pressure
⇌
Air Mixing
Mixed-air temp & % outdoor air
Field Sizing
🌀
Fan Laws
Speed vs. CFM, SP & BHP
💧
Pump Affinity
Speed vs. GPM, head & BHP
▭
Duct Sizer
Size, velocity & friction rate
⬭
Pipe Sizer
Size by GPM with velocity
🔥
Gas Pipe Sizer
Capacity by length & size
Code & Comfort
♻️
Air Changes/Hr
ACH from CFM & room volume
🏢
Ventilation 62.1
Outdoor-air rate (single zone)
🌡️
Psychrometrics
Air properties from DB/WB
🔊
dB Add/Subtract
Combine sound levels
UNIT CONVERTER
Category
Value
From
To
RULES OF THUMB — COOLING & HEATING
Building / space type
Conditioned area
(ft²)
CHW ΔT
°F
HHW ΔT
°F
Heat
BTU/h·ft²
VELOCITY / CFM / AREA
Solve for
CFM
Velocity
Area / Size
Airflow
CFM
Velocity
FPM
Round dia.
in (optional)
or Area
ft²
Enter a round diameter
or
a duct area. Diameter fills area automatically.
AIR MIXING — MIXED-AIR TEMP & % OA
Outdoor air
CFM
OA temp
°F
Return air
CFM
RA temp
°F
FAN LAWS
Design RPM
Design CFM
Design SP
in w.g.
Design BHP
New operating point — set by
New RPM
New CFM
New RPM
New CFM (target)
PUMP AFFINITY LAWS
Design RPM
Design GPM
Design Head
ft
Design BHP
New RPM
AIR CHANGES PER HOUR
Solve for
ACH
Required CFM
Airflow
CFM
Target ACH
Floor area
ft²
Ceiling ht
ft
SOUND LEVELS — ADD & SUBTRACT (dB)
Add (combine)
Subtract
Levels to combine
dB, comma-separated
Total
dB
Remove source
dB
DUCT SIZER — ROUND
Airflow
CFM
Run length
ft (opt)
Round diameter
in
SIZE TABLE
PIPE SIZER
Flow
GPM
Run length
ft (opt)
Material
Fluid
Water
Propylene Glycol
Ethylene Glycol
Glycol
% mass
Fluid temp
°F
SIZE TABLE
GAS PIPE SIZER — NFPA 54
Connected Load
Flow (CFH)
Connected load
BTU/h
Run length
ft
Pressure drop
0.3" w.c.
0.5" w.c.
1.0" w.c.
Material
Sch 40 Steel
CSST (approx)
Heating value
BTU/ft³
CAPACITY TABLE
(CFH)
VENTILATION — ASHRAE 62.1 (SINGLE ZONE)
Space type
Rp
cfm/person
Ra
cfm/ft²
Floor area
ft²
People
Pz
Air distribution effectiveness — Ez
PSYCHROMETRICS
Dry bulb
°F
Wet bulb
°F
Site elevation
ft above sea level