S&P 500 position size calculator

Size an S&P 500 trade from your risk and a stop in index points — $1 per point per lot by default, or the contract your broker uses.

Updated 31 October 2026

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How sizing works on the S&P 500

SPX500 — US500 or SP500 at many brokers — is a CFD on the S&P 500 index of large US companies, priced in US dollars. The calculator measures the stop in index points and starts from a contract of 1 per point: one lot gains or loses $1 per point, 0.01 lot $0.01. The contract varies by broker — $10 per point instead of $1, for example — and the lot size scales with the contract, so check it before the first trade. A USD account needs no conversion; other account currencies use the rate you type or a reference rate from 27 September 2026, labelled an estimate.

A worked example: 0.5% of $25,000

A $25,000 account risking 0.5% — a common practice, not a rule — has $125 to lose. With a 12-point stop and the default contract, one lot loses 12 × $1 = $12, so the raw size is 125 ÷ 12 = 10.417 lots, rounded down to 10.41 lots and an actual risk of $124.92.

At a broker with $10 per point, type 10 into the contract size field: one lot now loses $120, the raw size is 1.042 and the position 1.04 lots, risking $124.80. Ten times the contract, a tenth of the lots, the same money at risk.

Points, percent and typical stops

The S&P 500 moves fewer points than the Nasdaq 100 because its price is lower: at 6,700 a 1% move is 67 points, against about 245 on the Nasdaq at 24,500. It is also usually the calmer of the two in percentage terms. Intraday stops of 8 to 25 points are common; around US inflation data, the jobs report and Federal Reserve decisions the index can cover that distance in a minute. The cash open at 09:30 New York and the last hour before 16:00 tend to be the busiest periods.

Index hours and the New York Kill Zone

US stocks trade from 09:30 to 16:00 New York time, and the CFD follows index futures outside those hours. The New York AM Kill Zone, 07:00–10:00, takes in the 08:30 data releases and the first half hour of the cash session; the London Kill Zone (02:00–05:00) and the Asian Kill Zone (20:00–00:00) trade on overnight futures volume and are usually quieter. See the windows in your time zone with the Kill Zone converter; today's sessions and news are on the S&P 500 market page.

Common S&P 500 sizing mistakes

• Assuming every broker's US500 is $1 per point. At $10 per point, a size worked out for $1 risks ten times the plan.
• Reusing a Nasdaq lot size. With the same contract, a 1% stop is about 67 points here and 245 there, so the lots for the same risk are very different.
• Counting the stop in MT5 points when the symbol has one or two decimals: with one decimal, 120 MT5 points are 12 index points — check your symbol's decimals.
• Sizing at 09:29 on a pre-open spread and holding through the open, when slippage can add to the loss per lot.

For the tech index use the NAS100 calculator; the general method is in how to calculate position size.