Position health

The narrative is on how it works. Try the numbers first:

Position health calculator

Market

NVDA / USDGSPY / USDGWETH / USDGSPCX / USDGTSLA / USDGMSFT / USDGAAPL / USDGQQQ / USDGGOOGL / USDGAMD / USDG

LTV 60% · liquidation threshold 65% · bonus 8% · borrow APR 0.500%

Collateral (NVDA)

NVDA price

USD

Debt

USDG

Days of interest

Not liquidatable

Health factor

1.2253

Collateral value

$4,528.62

Max borrow (LTV)

2,717.17 USDG

Room to borrow

314.88 USDG

Liquidation price

$184.79

Drop to liquidation

18.39%

Bad debt if fully liquidated below

$129.72

Withdrawable NVDA

2.317679

bad debt below $129.72liquidation $184.79price now $226.43

Values in USD

Health checks convert both sides to USD scaled by $10^{18}$, rounding down at every step:

$$\hat p = \left\lfloor \frac{p \cdot 10^{18}}{10^{d_o}} \right\rfloor, \qquad CV = \left\lfloor \frac{q\,\hat p_c}{10^{d_c}} \right\rfloor, \qquad BV = \left\lfloor \frac{d\,\hat p_b}{10^{d_b}} \right\rfloor$$ $$M_{\text{LTV}} = \left\lfloor \frac{CV \cdot \text{LTV}}{10^{18}} \right\rfloor, \qquad M_{\text{LT}} = \left\lfloor \frac{CV \cdot \text{LT}}{10^{18}} \right\rfloor$$

Where:

• $p$ — the oracle price, with $d_o = 8$ decimals; $\hat p$ is USD per whole token × $10^{18}$.
• $q$ — the collateral in the Position, Position.totalCollateral(), with $d_c$ decimals (18). A Position holds its market's collateral token and nothing else.
• $d$ — the borrower's debt, $\lfloor s \cdot \text{TBA} / \text{TBS} \rfloor$ (shares), with $d_b$ decimals (USDG: 6).
• $\text{LTV}$, $\text{LT}$ — loan-to-value and liquidation threshold, WAD.
• $M_{\text{LTV}}$, $M_{\text{LT}}$ — the most debt value the collateral supports for borrowing, and before liquidation.

Source: IsHealthy · 0x9259…F9a1. Prices come from the TokenDataStream. It keeps serving the last price while the market is closed, so health can be computed over a weekend, and it reverts in the fault states (stale in session, past the hard cap, paused, invalid) — see oracles and market hours.

Two limits

A borrow, or a collateral withdrawal from a Position with debt, must leave

$$BV \le M_{\text{LTV}}$$

or it reverts ExceedsMaxLTV (IsHealthy · 0x9259…F9a1). Both checks use the debt after accrual. With no debt, the check passes.

A position is liquidatable when

$$BV > M_{\text{LT}}$$

strictly (IsHealthy · 0x9259…F9a1). A position exactly at the threshold is not liquidatable. Because $\text{LTV} \le \text{LT}$ is enforced at market creation, a position that just borrowed can never be liquidatable in the same transaction.

Health factor

The contracts do not compute a health factor. The usual one is

$$HF = \frac{M_{\text{LT}}}{BV} = \frac{q \cdot P_c \cdot \text{LT}}{d \cdot P_b}$$

with $P$ in USD per whole token. Liquidatable exactly when $HF < 1$. With no debt, HF is unbounded.

Max borrow

$$d_{\max} = \left\lfloor \frac{M_{\text{LTV}} \cdot 10^{d_b}}{\hat p_b} \right\rfloor, \qquad \text{room} = d_{\max} - d$$

A new borrow also has to pass the market's max utilisation (100%: the vault cannot be lent out entirely) and, if set, its borrow cap; neither binds for the position in the example below. Debt keeps growing between the moment you read it and the moment a transaction lands, so borrowing the whole room can revert — leave a margin.

Liquidation price

The collateral price at which $HF = 1$:

$$P^{\text{liq}}_c = \frac{d \cdot P_b}{q \cdot \text{LT}} \qquad\text{(liquidatable when } P_c < P^{\text{liq}}_c\text{)}$$

The contracts have no such function; it is derived from the inequality above. The distance to it is $1 - P^{\text{liq}}_c / P_c$. A position borrowed right up to its LTV sits $1 - \text{LTV}/\text{LT}$ above its liquidation price: 7.7% for NVDA/USDG, 6.7% for SPY/USDG, 6.25% for WETH/USDG, 10% for SPCX/USDG, TSLA/USDG and AMD/USDG, 7.1% for QQQ/USDG; MSFT/USDG, AAPL/USDG and GOOGL/USDG are NVDA/USDG's 7.7%.

A second price matters to lenders: below

$$P^{\text{bad}}_c = \frac{d \cdot P_b \cdot (1 + b)}{q}$$

a full liquidation takes all the collateral and still leaves debt — see bad debt.

Withdraw limit

With debt, the collateral left behind must still satisfy the LTV limit (not the liquidation threshold):

$$q'_{\min} = \left\lceil \frac{BV \cdot 10^{d_c} \cdot 10^{18}}{\hat p_c \cdot \text{LTV}} \right\rceil$$

and, on every market, the withdrawal needs Fresh prices while the Position has debt — see market hours. With no debt, all collateral can be withdrawn at any time. Source: Position, LendingPoolRouter.

Worked example

The illustrative Position on NVDA/USDG: 20 NVDA collateral and 2400000000 borrow shares, with $\text{TBA} =$ 20010000000 and $\text{TBS} =$ 20000000000. NVDA at $226.43088402, its mainnet price at block 86868761; USDG at $1. The amounts are illustrative; the price and parameters are mainnet's.

The second row books the market's pending 9.117741 USDG of interest from accrual first, as every check does. With that debt:

The calculator above starts at these inputs.