# Felix USA500 Open interest Methodology

## 1. Overview

This page covers the USA500 market (`flx:USA500`) on Felix, one of the markets deployed under the `flx` namespace on Hyperliquid HyperCore. The calculation is identical across all Felix markets; the figures on this page are scoped to the USA500 market.

Open interest measures the total USD notional value of all open positions on Felix at a point in time. It is a leading indicator of speculative activity and capital at risk, complementary to trading volume. Outstanding contracts across all perpetual markets are tracked continuously. Positions that have already been closed or liquidated within the period are excluded.

## 2. Data sources

- **Blockchain events**: `node_fills` events from Hypercore, covering the Hypercore chain

## 3. Step-by-step calculation

### Component A: Net position change tracking

- **Purpose**: Calculate the daily net change in position size for each trader and market
- **Logic**: `node_fills` events from Hypercore are filtered to isolate Felix perpetual markets. For each trade, the net change in position size is determined based on the trade side, where buy trades increase the position and sell trades decrease the position. These net changes are aggregated daily per trader and market.
- **Key fields**: `trader_address`, `market_id`, `side`, `size`

### Component B: Running position and open interest unit calculation

- **Purpose**: Determine the total outstanding contract units for each market
- **Logic**: A running position is calculated for each trader and market by taking the cumulative sum of daily net position changes over time. These running positions are forward-filled across days to ensure inactive days do not reset the position. The total open interest units per market are calculated by summing the absolute values of all active trader positions and dividing by two to represent a one-sided contract count.
- **Key fields**: `running_position`, `oi_units`

### Component C: Mark price determination

- **Purpose**: Establish the daily valuation price for each market asset
- **Logic**: Because Felix markets are settled in Hyper USD, the trade execution price is utilized directly as the USD value. The end-of-day mark price is defined as the latest observed fill price for each asset on a given day. These prices are forward-filled across days with no trading activity to maintain continuous valuation.
- **Key fields**: `price`

### Component D: USD valuation and aggregation

- **Purpose**: Convert open interest units to USD and aggregate to the product level
- **Logic**: Open interest units for each market are multiplied by the corresponding end-of-day mark price to calculate the USD open interest. Market identifiers are mapped to canonical product IDs by removing non-alphanumeric characters and lowercasing. The final values are aggregated daily by product and chain, with forward-filling applied to maintain continuous metrics.
- **Key fields**: `oi_units`, `price`, `product_id`

## Comparability note (one-sided convention)
One-sided open interest is reported (where each matched contract is counted once). Approximately double this figure is reported by platforms utilizing a two-sided open interest convention.

*This methodology was automatically generated by Token Terminal's methodology analyzer.*

Total USD notional value of all open positions on a derivatives protocol at a point in time.

Open interest

Derivative markets

Felix issues feUSD and USDhl and deploys perpetual markets under the flx namespace on Hyperliquid's HyperCore order book.

Felix combines stablecoin issuance with USDC-settled perpetual contracts on equities, commodities, indices, and crypto.

Felix is a protocol and product suite on Hyperliquid that spans stablecoins and HIP-3 perpetual markets.

USA500 PerpetualUSA500

Open interest

Open interest

Chain breakdown