Distance Tracking API: Walking, Running and Activity Distance by Platform

Distance is the metric where Apple and Google disagree on shape before they disagree on units. On Android, in the cloud and on the watch, a distance is a distance: one type, whatever the activity. On iOS the activity is part of the type, so a run and a ride write to different identifiers, and a daily total is a decision about which identifiers to add.

One type or nine#

HealthKit's nine distance identifiers, each a cumulative quantity in length units, with the iOS version Apple's documentation gives:

Read from Apple's documentation on 2026-10-02. Everywhere else it is one type: Health Connect's DistanceRecord "Captures distance travelled by the user since the last reading"; the Google Health API's distance is "Distance traveled over an interval of time"; and Wear OS Health Services' DataType.DISTANCE is "A distance delta between each reading expressed in meters."

Wear OS adds a split of its own, by terrain rather than activity: FLAT_GROUND_DISTANCE, INCLINE_DISTANCE and DECLINE_DISTANCE, each a distance in meters between readings. Google does not state that the three add up to DISTANCE, so do not add them to it, or check one against the other, without testing on a device.

Units and limits per value#

Two consequences. Google's integer millimeters need converting before anything is displayed. And Health Connect's per-record cap is why Google's own reference says, "If break downs are preferred in scenario of a long workout, consider writing multiple distance records."

How each one is read#

• Google Health API: an Interval record with a 1-minute storage resolution, listed for list, reconcile, rollup and dailyRollup, with webhook support and true-zeros support, which Google's table key defines as recording "explicit zero values to differentiate between an active zero value (such as zero active minutes) versus missing or unrecorded data." Google's table lists 28 compatible devices, and its migration table maps the Fitbit Web API's distance data to this type.
• Health Connect: an Interval record whose description gives the arithmetic: "The total distance over an interval can be calculated by adding together all the values during the interval." It also gives the writing rule, "The start time of each record should be equal to or greater than the end time of the previous record," which keeps consecutive records from overlapping. Reads need android.permission.health.READ_DISTANCE.
• Wear OS: a delta per update during an exercise, under the ACTIVITY_RECOGNITION permission in Google's permissions table. A daily form, DISTANCE_DAILY, also exists and is a row on the data-type table without a page here.
• HealthKit: cumulative, so .cumulativeSum in a statistics query, per identifier.

Where the number came from#

Google's description of the Health Services DataType class says it plainly: the data type "defines only the representation and format of the data, and not how it's being collected," and "As an example, DISTANCE may come from GPS location if available, or steps if not available." Treat any distance as an estimate of unknown method unless the source tells you more.

HealthKit lets a writer attach context as metadata. HKMetadataKeyLapLength goes "on a workout, workout segment, or a quantity sample that represents distance," and HKMetadataKeyIndoorBikeDistance holds "The workout distance displayed by a connected GymKit exercise bike." For the route itself rather than the total, see the GPS activity API guide.

Bluetooth sensors report distance inside larger characteristics rather than as a type of its own: the RSC Measurement characteristic's optional Total Distance is in units of a tenth of a meter, and a treadmill's Treadmill Data reports total distance in meters since the session began.

Traps#

• Choosing which Apple distances make a day. A cross-platform "distance today" has to decide whether cycling, swimming, wheelchair and the iOS 18.0 sports count. Write that rule down; Health Connect and Google will not make it for you, because they never split them.
• A test result is not a distance travelled. HealthKit's sixMinuteWalkTestDistance "stores the distance a user can walk during a six-minute walk test" and is discrete, not cumulative. Leave it out of totals.
• More than one writer. Where a phone and a watch both write distance, the double-counting trap the step counting API guide describes for steps applies; read each platform's aggregate rather than summing raw records from every source.
• Unit conversion at the edges. Millimeters from Google, meters from Wear OS and Health Connect's Length, a unit you picked on iOS: convert once, at ingestion, and store the unit.

Before you ship#

Re-check the identifier pages and the record and type references before each release; they regenerate from Apple's and Google's documentation. Decide your daily-total rule for Apple's nine types. Split long Health Connect writes into several records, keep them non-overlapping, and treat Wear OS's terrain split as its own measure, not a check on the total.