---
title: Units and quantities
framework: healthkit
role: collectionGroup
role_heading: API Collection
path: healthkit/units-and-quantities
---

# Units and quantities

Objects used to specify a quantity for a given unit, and to convert between units.

## Topics

### Units and quantities

- [Defining and converting units and quantities](healthkit/defining-and-converting-units-and-quantities.md)
- [HKQuantity](healthkit/hkquantity.md)
- [HKUnit](healthkit/hkunit.md)
- [HKMetricPrefix](healthkit/hkmetricprefix.md)

## See Also

### Basic samples

- [HKCumulativeQuantitySample](healthkit/hkcumulativequantitysample.md)
- [HKDiscreteQuantitySample](healthkit/hkdiscretequantitysample.md)
- [HKQuantitySample](healthkit/hkquantitysample.md)
- [HKCategorySample](healthkit/hkcategorysample.md)
- [HKCorrelation](healthkit/hkcorrelation.md)
- [Metadata Keys](healthkit/metadata-keys.md)