Tick size

What it is

Tick size is the smallest legal price increment an instrument can move. For US equity index futures, ES (E-mini S&P 500) has a tick size of $0.25 — prices can move from 5230.00 to 5230.25 to 5230.50, but never to 5230.10. NQ (E-mini Nasdaq-100) also uses $0.25. The 30-year Treasury futures (ZB) use 1/32 of a point. Crude oil (CL) uses $0.01. Each contract's tick size is set by its exchange and is immutable for that contract.

The closely related concept is tick value — the dollar P&L produced by one tick of price movement on one contract. ES has a tick value of $12.50 (one tick × the $50 multiplier ÷ 4 ticks per point). NQ has a tick value of $5.00 ($0.25 × $20 multiplier). MES, the micro version, has a tick value of $1.25 ($0.25 × $5 multiplier).

Together, tick size and tick value define the fundamental risk unit of a contract. Every trade's P&L is some integer number of ticks times the tick value times the position size.

Why it matters

Tick size and tick value are the inputs to every quantitative trading decision. Position sizing math relies on them: "I want to risk $500 on this trade, my stop is 8 ticks away, the tick value is $12.50, so I trade 500 / (8 × 12.50) = 5 contracts." Every R-multiple calculation, every stop distance translation, every target placement uses the tick value as its dollar-conversion factor.

For order flow and footprint analysis, tick size determines the resolution of per-price-level data. ES's $0.25 tick size means a typical bar might touch 8–20 distinct price levels; CL's $0.01 tick size means an active bar can touch 50+ levels. This affects how footprint charts are read: ES footprints are visually compact, CL footprints sprawl.

Tick size also affects how spread costs scale. A one-tick wide spread on ES costs $12.50 per contract round-trip; the same one-tick spread on MES costs $1.25; on a fixed-spread instrument like CL it depends on the bid/ask gap rather than tick width.

How it appears on Sierra Chart

Sierra Chart stores tick size and tick value as part of each symbol's instrument metadata, set automatically when the symbol is loaded from the data feed. The platform uses these values internally for all price-axis rendering, order entry, and per-tick studies. Most studies and tools that need to convert ticks to dollars (or vice versa) read these values directly from the symbol — there is no need to hardcode multipliers.

For ACSIL developers, the tick size is exposed via sc.TickSize and the tick value via sc.CurrencyValuePerTick. Any study that needs to do dollar-aware math should read both rather than assuming an instrument-specific constant.

Common patterns / pitfalls

• Tick value ≠ tick size × multiplier in all cases — for most equity index futures the relationship is tick value = tick size × big-point multiplier, but for instruments with non-standard contract structures (some FX and rate futures) the relationship is exposed directly via tick value, not derivable.
• Always read from the symbol — never hardcode "$12.50 per tick" in a study. Symbol metadata changes (especially as exchanges adjust contracts) and hardcoded constants silently rot.
• Tick size affects backtesting — a slippage assumption of "0.5 ticks" means different dollar amounts on different contracts. Slippage models should be in tick units, not dollar units.
• Sub-tick prices are illegal — orders placed at sub-tick prices are rejected by the exchange. Some studies that compute target levels by formula need to round to tick size.
• DOM price levels are tick-spaced — the depth ladder shows one price per tick.

Related SCS studies

Trade Manager reads tick size and tick value from each instrument symbol to compute position sizes correctly regardless of whether you're trading ES, MES, CL, NQ, or any other futures contract. The Trading Journal records fills with their exact tick-rounded prices and computes P&L from the per-symbol tick value.