---
title: "S&P MidCap 400: Methodology"
description: "S&P MidCap 400 is maintained by S&P Dow Jones Indices and covers u.s. mid-cap equities. How the index selects and weights its constituents, and what that means for what it measures."
canonical: https://www.getswoopr.com/stocks/indexes/sp-midcap-400/
source: "Swoopr Investment: https://www.getswoopr.com"
---

# S&P MidCap 400: What It Measures and How It Is Built







## Direct Answer



> The S&P MidCap 400 is a rule-based measurement of u.s. mid-cap equities, maintained by S&P Dow Jones Indices. Like every index it owns nothing: it is a number produced by applying a published weighting formula to a selected list of companies, revised on a schedule the provider sets.








## What this index covers



The S&P MidCap 400 covers u.s. mid-cap equities, within the United States market. S&P Dow Jones Indices defines which securities are eligible, how they are selected from that pool, and how much each one contributes to the published number.



The name states a target of 400 companies. A target is not a guarantee of the exact count on any given day: corporate actions, dual share classes and pending additions all move the real number around it.








## How constituents are weighted



Swoopr has not verified the weighting method for this index against S&P Dow Jones Indices's current methodology document, so none is stated here rather than guessed. The provider link below is authoritative.








## Current S&P MidCap 400 constituents



S&P Dow Jones Indices publishes and licenses the S&P MidCap 400 constituent list. Swoopr does not republish it here. The provider's own page is the authoritative source for current membership and weights.



[S&P Dow Jones Indices: official S&P MidCap 400 page](https://www.spglobal.com/spdji/)








## Related reading



- [All stock market indexes](https://www.getswoopr.com/stocks/indexes/): how indexes are built, weighted and revised.
- [United States indexes](https://www.getswoopr.com/stocks/indexes/us/): others covering the same region.
- [Index concentration](https://www.getswoopr.com/technical-analysis/market-concentration/index-concentration/): measuring how much of an index sits in its largest holdings.
- [Index rebalancing and inclusion effects](https://www.getswoopr.com/stocks/corporate-actions-catalysts/index-rebalancing-and-inclusion-effects/): what happens to a stock when index membership changes.








## Frequently Asked Questions


### Who maintains the S&P MidCap 400?



S&P Dow Jones Indices maintains the S&P MidCap 400 and publishes the methodology document that defines its eligibility and weighting rules.




### What does the S&P MidCap 400 measure?



It measures u.s. mid-cap equities. The index is a calculated number applying a weighting formula to a selected list of companies, and it holds nothing itself.




### Where can I see the current S&P MidCap 400 constituents?



S&P Dow Jones Indices publishes the current constituent list. Swoopr does not republish it, because index providers license constituent data and Swoopr holds no such licence.











## About the author



The [Swoopr Editorial Team](https://www.getswoopr.com/authors/swoopr-editorial-team/) writes Swoopr Investment's educational library, covering market structure, analysis methods and the mechanics behind the numbers investors read every day.



Our [editorial policy](https://www.getswoopr.com/legal/editorial-policy/) and [corrections policy](https://www.getswoopr.com/legal/corrections-policy/) set out how this content is produced, reviewed and fixed when it is wrong.