Calculator Inputs
Enter either altitude or pressure, choose a mode, and adjust atmosphere assumptions when needed.
Pressure–Altitude Trend Graph
The line shows the modeled atmosphere profile using your selected baseline inputs. The marker highlights the current result.
Example Data Table
These sample values use a standard sea-level pressure of 1013.25 hPa and sea-level temperature of 15 °C.
| Altitude (m) | Altitude (ft) | Pressure (hPa) | Pressure (psi) | Temp (°C) | Density (kg/m³) | Layer |
|---|---|---|---|---|---|---|
| -500 | -1,640 | 1,074.776 | 15.5883 | 18.25 | 1.28490 | Troposphere |
| 0 | 0 | 1,013.250 | 14.6959 | 15.00 | 1.22501 | Troposphere |
| 1,000 | 3,281 | 898.745 | 13.0352 | 8.50 | 1.11165 | Troposphere |
| 2,500 | 8,202 | 746.823 | 10.8318 | -1.25 | 0.95687 | Troposphere |
| 5,000 | 16,404 | 540.195 | 7.8349 | -17.50 | 0.73612 | Troposphere |
| 10,000 | 32,808 | 264.359 | 3.8342 | -50.00 | 0.41270 | Troposphere |
| 15,000 | 49,213 | 120.443 | 1.7469 | -56.50 | 0.19367 | Lower Stratosphere |
| 20,000 | 65,617 | 54.747 | 0.7940 | -56.50 | 0.08803 | Lower Stratosphere |
Formula Used
Troposphere equation
For altitudes up to 11,000 meters, the calculator uses:
T = T0 - Lh
P = P0 × (T / T0)g / (R × L)
ρ = P / (R × T)
Lower stratosphere equation
From 11,000 to 20,000 meters, the model assumes constant temperature:
P = P11 × exp[-g(h - 11000) / (R × T11)]
ρ = P / (R × T11)
Inverse formulas
When pressure is known, altitude is recovered with:
h = (T0 / L) × [1 - (P / P0)(R × L) / g] for the troposphere.
h = 11000 - (R × T11 / g) × ln(P / P11) for the lower stratosphere.
Symbols: P is pressure, T is temperature, ρ is density, L is lapse rate, g is gravity, and R is the specific gas constant.
How to Use This Calculator
- Choose whether you want altitude converted to pressure or pressure converted to altitude.
- Enter the known value and select the correct unit.
- Adjust sea-level pressure, sea-level temperature, or other atmosphere constants if your scenario differs from default ISA values.
- Press Calculate Now to display the result above the form.
- Review the converted value, atmospheric layer, density, and ratios.
- Use the export buttons to save a CSV sheet or a compact PDF report.
FAQs
1) What does this calculator convert?
It converts barometric pressure to altitude or altitude to barometric pressure using a standard-atmosphere model. It also estimates temperature, air density, and pressure, temperature, and density ratios from the same inputs.
2) Why are sea-level settings editable?
Editable sea-level pressure and temperature let you model custom baselines. That helps when you want sensitivity checks, lab demonstrations, or comparisons against a non-default reference atmosphere.
3) Is this suitable for aviation work?
It is useful for educational checks, planning, and quick comparisons. Certified flight operations should still rely on approved instruments, official weather reports, and validated aviation procedures.
4) Why does pressure drop with altitude?
Higher altitude means less air above a point. With less overlying air mass, the weight of the atmosphere decreases, so static pressure becomes lower.
5) What range does this page support?
This version supports calculations from -1,000 meters to 20,000 meters. The page uses a troposphere model below 11,000 meters and an isothermal lower-stratosphere model above that boundary.
6) Does the calculator include humidity effects?
No. It assumes dry air and uses a standard specific gas constant. Humidity can slightly change density and related values, but it is not included in this streamlined converter.
7) Why do my values differ from a weather station?
Real atmosphere conditions vary with weather systems, local temperature structure, humidity, and instrument calibration. This calculator is based on an idealized reference atmosphere, not a live observation feed.
8) What do the ratios mean?
Pressure, temperature, and density ratios compare the local state to your chosen sea-level baseline. Ratios make it easier to compare different operating points without changing units.