# How Long Will It Last?

> Estimate remaining life of appliances and home components and plan the replacement. Pick an appliance or home component, enter its age, how hard it is used and how well it is maintained. The tool uses the life-expectancy ranges published in InterNACHI's Standard Estimated Life Expectancy Chart for Homes to estimate remaining years, the share of life used, and a replacement planning window.

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://howlongwillitlast.usefulweb.site/ (interactive tool at https://howlongwillitlast.usefulweb.site/tool)
- JSON API: POST https://howlongwillitlast.usefulweb.site/api/v1/calculate with a JSON object of inputs (schema: https://howlongwillitlast.usefulweb.site/api/v1/tool)
- OpenAPI: https://howlongwillitlast.usefulweb.site/openapi.json
- MCP (Streamable HTTP): https://howlongwillitlast.usefulweb.site/mcp - tool `how_long_will_it_last`

## Inputs
- item (select): Item
- ageYears (number, required): Current age
- usage (select): Usage intensity
- maintenance (select): Maintenance quality

## Method
- Base range: the YEARS value for the item from InterNACHI's Standard Estimated Life Expectancy Chart for Homes (e.g. '9 to 13'). Single values use the same min and max; 'N+' values are open-ended (only a minimum).
- Adjusted range = base range × usage multiplier (light 1.15, normal 1.0, heavy 0.8) × maintenance multiplier (regular 1.0, occasional 0.9, neglected 0.75). These multipliers are this tool's own assumptions, not published figures; InterNACHI's values already assume regular recommended maintenance and normal wear and tear.
- Remaining years = max(0, adjusted min − age) to max(0, adjusted max − age).
- Life used = age ÷ midpoint of the adjusted range × 100 (open-ended: ÷ adjusted minimum).
- Status: < 50% early life, 50–80% mid-life, ≥ 80% but below adjusted minimum approaching end, between adjusted min and max within end-of-life range, beyond adjusted max beyond expected life.
- Replacement window = current year + remaining min … current year + remaining max (rounded to whole years).

## Limits
- Life expectancies are guidelines only, not guarantees or warranties (InterNACHI).