> ## Documentation Index
> Fetch the complete documentation index at: https://sdk.avantisfi.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Margin & Position Size

> Deposit or withdraw collateral, and add size to open positions.

## Adjust margin

Deposit lowers effective leverage and moves the liquidation price away; withdraw does the opposite.

```python theme={null}
pos = (await client.account.positions()).positions[0]

await client.trade.update_margin(pos.pair_index, pos.index, "deposit", 50)    # +50 USDC
await client.trade.update_margin(pos.pair_index, pos.index, "withdraw", 25)   # -25 USDC
```

Preview the effect before committing with [`compute.estimate_liquidation_price`](/data/compute).

## Increase position size

Adds collateral at a chosen leverage; the position's average open price is re-weighted.

```python theme={null}
await client.trade.increase_position(
    pos.pair_index, pos.index,
    collateral=100,          # additional USDC
    leverage=10,             # leverage applied to the added collateral
    slippage_percent=1,
)
```

| Parameter          | Default  | Notes                                             |
| ------------------ | -------- | ------------------------------------------------- |
| `collateral`       | required | Additional USDC                                   |
| `leverage`         | required | For the added collateral (not the whole position) |
| `open_price`       | `None`   | Resolved from the live feed when omitted          |
| `slippage_percent` | `1`      | Max slippage on the increase fill                 |

## Increase sized in coin units

Targets added coin exposure; fill leverage floats within bounds (all three leverage arguments are required):

```python theme={null}
await client.trade.increase_position_coin(
    pos.pair_index, pos.index,
    collateral=100,
    coin_exposure=0.25,      # ETH to add
    leverage=10,             # reference leverage, contract-required
    min_leverage=5,
    max_leverage=20,
)
```

<Note>
  To **reduce** size, use a partial [market close](/trading/market-orders#close). There is no separate decrease method.
</Note>