Ask a struggling 0DTE trader about their strategy and they'll describe entries. Ask about position sizing and you'll usually get a blank look. That's backwards — sizing is what keeps you in the game long enough for an edge to matter.

Assume zero

The core rule of 0DTE sizing: assume any single trade can go to zero, because it genuinely can within hours. Size every position so that outcome is survivable and unremarkable. If one bad 0DTE trade meaningfully dents your account, the position was too big — full stop.

Fixed-fractional risk

Risk a small, fixed fraction of your account per trade — the same percentage every time, so no single loss or short losing streak can end you (risk of ruin). This removes the emotional sizing that wrecks accounts: no doubling up to "make it back," no going huge on a "sure thing." Consistency of risk is the edge (position sizing basics).

You don't blow up a 0DTE account with a bad trade. You blow it up with a bad trade that was three times too big.

Let conviction scale size, not emotion

Sizing can vary with genuine conviction — a higher-quality setup can justify a larger (but still bounded) position — as long as the framework is defined in advance, not decided in the heat of a move. NoVo does exactly this: your allocation is fixed, and conviction tiers scale contract count within it, mechanically. See 0DTE risk management and 0DTE vs 1DTE.