---
title: 'Passive denominator | Plainrouter'
description: 'An arrival count used as a reference population when comparing conversion measurement.'
last_updated: 2026-09-10
---

# Passive denominator

A passive denominator is a reference count of arrivals against which a separate conversion count can be compared. It is not itself a conversion signal.

## Why keep the denominator separate?

A conversion total alone does not show how many arrivals were observed. Keeping arrivals separate lets a reader distinguish traffic volume from the portion that produced recorded conversions.

## Is it the same as an ad platform's reported traffic?

No. Systems may count at different boundaries and use different time windows. Compare the definitions and collection coverage before interpreting a difference as missing events.

## Does it authorize modeled conversions?

No. A reference count does not turn an estimate into verified revenue. Modeled data must not feed spend gates or kill switches.

## Related reading

- [Arrival definition](/definitions/arrival)
- [All definitions](/definitions)
- [Signals](/product/signals)
- [Actions](/product/actions)
- [Implementation guides](/library)
- [API documentation](https://plainrouter.com/docs/api/conversions)