# Subscription Stack

> Add up every subscription, spot overlaps and see which ones to cancel and what you save. List your subscriptions with price, billing cycle, category, how often you use them and how many people share them. Subscription Stack converts everything to monthly and yearly totals, groups by category, flags overlapping services, computes cost per use and lists cancellation candidates with the savings.

Part of usefulweb.site (https://usefulweb.site/). Results are deterministic calculations from the inputs and the listed assumptions; the API returns exactly what the web page shows.

## Use it
- Human interface: https://subscriptionstack.usefulweb.site/ (interactive tool at https://subscriptionstack.usefulweb.site/tool)
- JSON API: POST https://subscriptionstack.usefulweb.site/api/v1/calculate with a JSON object of inputs (schema: https://subscriptionstack.usefulweb.site/api/v1/tool)
- OpenAPI: https://subscriptionstack.usefulweb.site/openapi.json
- MCP (Streamable HTTP): https://subscriptionstack.usefulweb.site/mcp - tool `subscription_stack`

## Inputs
- currency (text): Currency - Shown in results only; no conversion is performed.
- minUsesPerMonth (number): Flag if used fewer than
- maxCostPerUse (number): Flag if cost per use is above - In your currency, for your share.
- subscriptions (table, required): Subscriptions - Price is the full price per billing period; “Shared by” splits it (you pay price ÷ people). Leave uses empty if unknown.

## Method
- Monthly price = weekly × (365.25/12)/7 (≈ 4.348), monthly × 1, quarterly ÷ 3, yearly ÷ 12.
- Your share = monthly price ÷ number of people sharing; annual = your monthly share × 12.
- Cost per use = your monthly share ÷ uses per month (not computed when uses are unknown or zero).
- Overlap = two or more subscriptions in the same category (excluding “other”).
- Cancel candidate if uses per month < your threshold, or cost per use > your threshold, or it is the most expensive per use (or least used) service within an overlapping category.
- Savings if cancelled = sum of your monthly shares of all candidates; annual = × 12.