# Car Heat Calculator (Temperature Inside a Parked Car)

URL: https://speedycalculator.com/calculators/health/car-heat/
Last updated: 2026-10-30

> The car heat calculator estimates how hot the inside of a parked car gets in the sun over time from the outside temperature, showing how quickly it becomes dangerous for children and pets.

## Inputs

- Outside temperature (°C, °F)
- Minutes parked in the sun

## Results

- Estimated temperature inside the car
- Rise over the outside temperature

## Formula

```
Interior temperature ≈ outside temperature + rise over time
Typical rise: +19 °F (11 °C) in 10 min, +29 °F (16 °C) in 20 min, +34 °F (19 °C) in 30 min, +43 °F (24 °C) in 60 min
```

## Explanation

Even on a mild 70 °F (21 °C) day, a car's interior can exceed 100 °F (38 °C) within 30 minutes. Opening the windows a little makes almost no difference. Children's bodies heat up three to five times faster than adults' – never leave a child or pet in a car.

### How to use the Car Heat Calculator

- **Outside temperature**
- **Minutes parked in the sun**

Results update as you type, and every field accepts the units shown in its menu.

### How it works

Enter the outside temperature and the time the car is parked.

### Inputs explained

FieldWhat to enterOutside temperatureUnits: °C, °FMinutes parked in the sunA number

### What each result means

- **Estimated temperature inside the car** = [Outside temperature] + interp([Minutes parked in the sun], 0, 10, 0, 19, 29, 34, 38, 41, 43, 45, 47, 49)÷1.8
- **Rise over the outside temperature** = [Estimated temperature inside the car] - [Outside temperature]

### Example values

How the main result changes when **Outside temperature** changes and everything else stays at the example values above:

Outside temperature (°C)Estimated temperature inside the car (°C)12.53118.7538254431.255037.5565069
*Health note: this calculator is for education and screening only and is not a diagnosis or treatment advice. Discuss your results with a qualified clinician.*

## Worked example

Inputs — Outside temperature: 25 °C; Minutes parked in the sun: 30.

Results — **Estimated temperature inside the car = 44 °C**; Rise over the outside temperature = 19 °C.

## Key terms

- **Heatstroke**: Life-threatening rise in body temperature.

## FAQ

**How fast does a car heat up?**
About 80% of the rise happens in the first 30 minutes.

**Does cracking the windows help?**
Hardly at all.

**What should I do if I see a child or pet in a hot car?**
Call emergency services immediately.


## Sources

- [McLaren C et al. Heat stress from enclosed vehicles: moderate ambient temperatures cause significant temperature rise. Pediatrics, 2005](https://pubmed.ncbi.nlm.nih.gov/15995019/)