> ## Documentation Index > Fetch the complete documentation index at: https://docs.derivadex.com/llms.txt > Use this file to discover all available pages before exploring further. # Price Feeds and Mark Price Inputs > DerivaDEX pricing reference for external spot sources, index-price aggregation, mark-price calculation, clamp bounds, and mark-dependent trading checks. DerivaDEX prices each perpetual with two related values: the **index price** (a composite spot price from external feeds) and the **mark price** (the fair price used for margin, liquidation, funding, and mark-relative trading checks). ## Price types and what they are used for | Price | Definition | Used for | | ---------------- | ------------------------------------------------------------------------------------- | -------------------------------------------------------------------------------------- | | Index price | Composite spot price from the configured external feeds | External reference input to the mark price | | Mark price | Index price plus a smoothed premium, clamped to `±50` basis points (`±0.5%`) of index | Margin, liquidation, funding, and price-band checks; fills still execute at book price | | Last trade price | Price of the most recent fill on the DerivaDEX order book | Trade reporting and chart displays | | Bankruptcy price | Price at which a strategy's collateral is fully consumed by position losses | Liquidation spread and auto-deleveraging (ADL) pricing | The **mark price** (not the **last trade price**) determines risk checks. ## Index sources by market By default, each listed perpetual uses three external spot feeds. | Market | Underlying | External spot sources | | ------ | ---------- | ------------------------------------------------------ | | `ETHP` | ETH | Coinbase `ETH-USD`, Binance `ETHUSDC`, Gemini `ETHUSD` | | `BTCP` | BTC | Coinbase `BTC-USD`, Binance `BTCUSDC`, Gemini `BTCUSD` | ## Index price calculation At each oracle update, typically once per second, DerivaDEX aggregates the latest source prices into one index price. ```text theme={null} median_source_price = median(latest_source_prices) clamped_source_i = clamp(source_i, 0.995 × median_source_price, 1.005 × median_source_price) clamped_composite = average(clamped_source_1 ... clamped_source_n) index_price_next = index_price_prev + alpha × (clamped_composite - index_price_prev) alpha = 2 / (30 + 1) ``` | Parameter | Value | Notes | | ------------------------------- | ----------------------------------: | -------------------------------------------------------------------- | | Aggregation method | Median anchor, then arithmetic mean | Outliers are clamped before averaging | | Per-source outlier clamp | `±0.5%` around the median | Applied separately to each source price | | EMA period | `30` updates | `alpha = 2 / (30 + 1)` | | Default oracle polling interval | `1` second | Source feeds are polled once per second in the default configuration | | First published index price | Current clamped composite | No time smoothing applies until there is a prior published value | ## Mark-price inputs The mark price starts from the current index price and adds a smoothed premium derived from the DerivaDEX book. | Input | Definition | Fallback behavior | | ----------- | -------------------------------------------------------- | -------------------------------------------------------------------------------------------------------------- | | Index price | Current composite spot price from the external feeds | Required base input | | Fair price | Best available book reference from DerivaDEX quotes | Midpoint if both sides exist; bid if only bid exists; ask if only ask exists; index price if the book is empty | | Premium EMA | Exponential moving average of `fair_price - index_price` | Carries forward the prior premium state between updates | ## Mark-price calculation The mark price uses the fair-price premium, then clamps the result back to the index. ```text theme={null} fair_price = (best_bid + best_ask) / 2 if both sides exist fair_price = best_bid if only bid exists fair_price = best_ask if only ask exists fair_price = index_price if the book is empty premium = fair_price - index_price premium_ema_next = premium_ema_prev + alpha × (premium - premium_ema_prev) mark_price = index_price + clamp(premium_ema_next, -0.005 × index_price, +0.005 × index_price) ``` | Parameter | Value | Notes | | ---------------- | ---------------------------------: | --------------------------------------------------------------------------- | | Premium input | `fair_price - index_price` | Tracks the DerivaDEX book relative to the external index | | EMA period | `30` updates | Uses the same smoothing constant as the index update | | Mark-price clamp | `±50` bps (`±0.5%`) of index price | Prevents the mark from drifting arbitrarily far from the external reference | | Realtime feed | `MARK_PRICE` | Carries mark-price and funding-rate updates | ## Mark-dependent trading checks DerivaDEX uses the current mark price in both sequencing and matching. | Check | What happens | | ---------------------------------- | ------------------------------------------------------------------------------------------------------------------------------------------------- | | Explicitly priced order validation | Sequencing rejects an explicitly priced order when its taker price breaches the product's `max_taker_price_deviation` from the current mark price | | Market-order handling | Market orders skip the sequencer deviation check because they have no explicit price | | Matching price band | When no explicit taker limit exists, matching derives a mark-price-relative limit from the product's `max_taker_price_deviation` | | Residual beyond the band | Any unmatched remainder is canceled rather than filled outside the effective band | | Missing mark price | Requests can fail with `MarketPriceNotAvailable` instead of trading without a current risk price | ## Worked pricing cases These examples show which book price becomes the fair-price input before the premium EMA and mark-price clamp apply. | Book state | Fair-price input | | ---------------------------------- | ------------------- | | Best bid `2,000`, best ask `2,002` | Midpoint `2,001` | | Best bid `2,000`, no ask | Bid `2,000` | | No bid, best ask `2,002` | Ask `2,002` | | No bid and no ask | Current index price | ## Related references Feed venues and polling intervals are governance-controlled and may change. * [Product and Trading Specifications](/reference-public/product-and-trading-specifications) * [Margin Requirements](/reference-public/margin-requirements) * [Funding Rate Logic](/reference-public/funding-rate-logic) * [Trading Safeties and Guards](/reference-public/trading-safeties-and-guards) * [Order and Account Event Reference](/reference-public/order-and-account-event-reference) * [Error Reference](/reference-public/error-reference)