Stack Effect Calculator
Pressure difference from indoor-outdoor temperature.
Enter your values
Enter the height above neutral plane in ft.
Enter the indoor temp in °F.
Enter the outdoor temp in °F.
Results update instantly as you type — no submit needed. Your values are remembered on this device, and the shareable link reopens the calculator with exactly these numbers.
- Stack pressure
- 0.111 in wc
- In Pa
- 27.65
- Direction
- Air rises and exits high, enters low
- Temperature difference
- 50 °F
Quick answer
Stack effect pressure rises with building height and the indoor-outdoor temperature difference.
ΔP = 0.0188 x h x (1/To - 1/Ti)
At a glance
| What it does | Pressure difference from indoor-outdoor temperature. |
|---|---|
| Category | HVAC & Airflow |
| Inputs needed | Height above neutral plane, Indoor temp, Outdoor temp |
| Main output | Stack pressure |
| Formula | ΔP = 0.0188 x h x (1/To - 1/Ti) |
| Cost | Free — no sign-up, no download |
How to use the Stack Effect Calculator
- 1Measure height from the neutral pressure plane, usually mid-height of the building.
- 2Enter indoor and outdoor temperatures for the worst-case day.
- 3Use the result to size vestibules, shaft dampers and pressurisation fans.
Inputs explained
- Height above neutral plane(ft)
- Enter the height above neutral plane in ft.
- Indoor temp(°F)
- Enter the indoor temp in °F.
- Outdoor temp(°F)
- Enter the outdoor temp in °F.
Worked example
Using the values the calculator loads with:
Inputs
- Height above neutral plane30 ft
- Indoor temp70 °F
- Outdoor temp20 °F
Results
- Stack pressure0.111 in wc
- In Pa27.65
- DirectionAir rises and exits high, enters low
- Temperature difference50 °F
Frequently asked questions
Why does the top floor overheat?
Stack effect pushes warm air upward and out, drawing cold air in low — the top floor stays warmest.
Does it reverse in summer?
Yes, weakly, when indoor air is cooler than outdoor air.
What do I need to enter into the Stack Effect Calculator?
Just 3 values: height above neutral plane, indoor temp, outdoor temp. Every field starts with a realistic example, so you can change one number at a time and watch the result update instantly.
How does the Stack Effect Calculator work out the answer?
Stack effect pressure rises with building height and the indoor-outdoor temperature difference. It applies the formula ΔP = 0.0188 x h x (1/To - 1/Ti) and shows the working so you can check each step by hand.
Is the Stack Effect Calculator free, and do I need an account?
It is completely free with no sign-up, no download and no usage limit. Everything is calculated in your browser, so the numbers you type never leave your device.
Results are estimates for general information. For medical, legal, structural or financial decisions, confirm with a qualified professional.