---
title: Frequent Guest Calculator
description: Estimate a frequent guest's proportional share of selected monthly household costs with a transparent person-day formula.
canonical: https://0.0.0.0:3000/
---

# Frequent Guest Calculator

Estimate a frequent guest's fair contribution to selected shared household costs.

## Method

The calculator uses person-days:

`guest ratio = guest nights / (regular residents × days in month + guest nights)`

That ratio is applied only to the monthly cost rows the user chooses to include.

This is a conversation baseline, not legal, lease, tax, or financial advice.

## Browser calculator

Human visitors can verify an email address with a 6-digit OTP and use the interactive calculator at https://0.0.0.0:3000/.

## Agent interfaces

- OpenAPI: https://0.0.0.0:3000/openapi.json
- Human API docs: https://0.0.0.0:3000/api-docs
- API catalog: https://0.0.0.0:3000/.well-known/api-catalog
- MCP server card: https://0.0.0.0:3000/.well-known/mcp/server-card.json
- MCP endpoint: https://0.0.0.0:3000/mcp
- Agent Skills: https://0.0.0.0:3000/.well-known/agent-skills/index.json
- ARD manifest: https://0.0.0.0:3000/.well-known/ard.json

## Calculation API

POST https://0.0.0.0:3000/api/calculate with JSON containing:

- residents: integer, 1-12
- guestNights: integer, 0-31 and no greater than daysInMonth
- daysInMonth: 28, 29, 30, or 31
- costs: array of objects with label, amount, and included

The response includes the guest ratio, included total, estimated contribution, and per-cost breakdown.