Understanding Temperature at Altitude
Air gets colder as you climb — that is one of the most reliable patterns in the atmosphere. This calculator applies the International Standard Atmosphere (ISA) model, the reference model used in aviation, meteorology, and engineering, to estimate the temperature at a given altitude from a sea-level starting temperature and a lapse rate.
The formula
Within the troposphere (roughly the lowest 11 km / 36,089 ft of the atmosphere), temperature falls in a straight line as altitude increases:
- T = T0 − L × h
- T0 is the sea-level (h = 0) temperature.
- L is the lapse rate, the rate temperature falls per unit of altitude — the ISA standard value is 6.5°C per 1,000 m.
- h is altitude above sea level.
Above the tropopause (about 11 km) and up to roughly 20 km, the ISA model treats the lower stratosphere as isothermal — temperature stays essentially constant near −56.5°C rather than continuing to fall. This calculator applies the linear formula below 11 km and holds the tropopause temperature constant above it.
Standard atmosphere reference values
- Sea-level standard temperature: 15°C (59°F, 288.15 K).
- Standard lapse rate: 6.5°C per 1,000 m (about 3.57°F per 1,000 ft) in the troposphere.
- Tropopause altitude: about 11,000 m (36,089 ft), where standard temperature is −56.5°C (216.65 K).
Why temperature drops with altitude
As altitude increases, air pressure and density decrease. Rising air expands and cools, and the atmosphere is heated mainly from below (by the sun-warmed ground and ocean), so the effect weakens with height. The 6.5°C/1,000 m figure is an average of many real-world soundings and is close to, but not identical to, the dry adiabatic lapse rate (about 9.8°C/1,000 m) that describes a single unsaturated air parcel rising on its own.
Frequently Asked Questions
What is the standard temperature lapse rate?
What formula does this calculator use?
Why does temperature stop falling above about 11 km?
Does this account for humidity or real weather conditions?
Common Tip Percentages
| Service | Typical Tip Range | Notes |
|---|---|---|
| Restaurant (sit-down) | 15–20% | 20%+ for exceptional service |
| Food delivery | 10–20% | Consider extra for long distances |
| Taxi / rideshare | 10–20% | More for assistance with luggage |
| Hotel housekeeping | $2–5/night | Leave daily, not just at checkout |
| Barber / hair salon | 15–20% | On pre-discount total |
| Pizza delivery | 10–15% or $3–5 minimum | Higher in bad weather |
General Household Budget Ratios (50/30/20 Rule)
| Category | % of Net Income | Examples |
|---|---|---|
| Needs | 50% | Rent, groceries, utilities, insurance |
| Wants | 30% | Dining out, entertainment, hobbies |
| Savings / Debt | 20% | Emergency fund, retirement, extra payments |
Common Measurement Conversions for Everyday Use
| Quantity | US / Imperial | Metric Equivalent |
|---|---|---|
| 1 cup | 8 fl oz | 237 mL |
| 1 pint | 16 fl oz | 473 mL |
| 1 quart | 32 fl oz | 946 mL |
| 1 gallon | 128 fl oz | 3.785 L |
| 1 lb | 16 oz | 453.6 g |
| 1 ft | 12 in | 30.48 cm |