Trading cost calculator

Your numbers

The planned or actual entry.

Sets 1R, the dollars at risk, which the cost is measured against.

To see the cost as a share of the planned move.

The number of shares bought (or sold short) and later closed.

Charged on the entry and again on the exit. Enter 0 for commission-free trading.

The gap between the ask and the bid, per share, in dollars.

How far the average fill lands from the quote, per share, on each side.

To see the cost over a year of similar trades.

Results

Cost per round trip in R
0.032R
Cost per round trip
$8.00
Cost as % of the target move
1.33%
Cost as % of position value
0.16%
Cost per year
$800.00
Cost per year in R
3.20R

An educational tool: an estimate from the costs you enter. Actual spreads and slippage vary with the stock, the time of day and the order size, and gaps can add more. Nothing you enter is sent or saved. Not investment advice.

How to use it

  1. Enter the entry, the stop and the share count. Add the target to compare the cost with the planned reward.
  2. Enter the commission per order, the stock’s typical bid-ask spread and your average slippage per share. Your journal’s fills compared with the quoted prices are the best source for slippage.
  3. Read the cost in R: it comes off the result of every trade, winner or loser. Add the number of round trips per year to see the annual total, and compare the cost in R with the system’s expectancy in R.

The formula

Cost per round trip = 2 × commission + shares × spread + 2 × shares × slippage. Buying at the ask and selling at the bid each cost half the spread against the mid price, so the full spread is paid once per round trip; commission and slippage apply on each side.

Cost in R = cost ÷ (shares × |entry − stop|), cost as % of the target move = cost ÷ (shares × |target − entry|) and cost as % of position value = cost ÷ (shares × entry).

Cost per year = cost per round trip × round trips per year, in dollars and in R. Regulatory and exchange fees on sales, borrowing costs on shorts and gaps through the stop are not included.

Worked example

Illustrative numbers: 100 shares bought at $50 with a stop at $47.50 and a target at $56, $1 commission per order, a $0.02 spread and $0.02 slippage per side. The round trip costs 2 × $1 + 100 × $0.02 + 2 × 100 × $0.02 = $8: 0.032R, 1.3% of the $600 target move and 0.16% of the $5,000 position. At 100 round trips a year that is $800, or 3.2R.

A short-term system with the same costs per share looks different: 500 shares at $50 with a stop at $49.50 and a target at $51 cost $32 per round trip, about 0.13R and 6.4% of the target move. At 500 round trips a year that is $16,000, or 64R. An expectancy of +0.2R per trade before costs would shrink to about +0.07R.

Questions

How do I calculate slippage?

Compare each fill with the price you expected when the order was sent, such as the quote or the stop price, and multiply the difference per share by the shares. Averaging it over many trades in your journal gives a realistic figure to enter here, per share and per side.

What does a commission-free trade still cost?

The bid-ask spread and slippage remain: a market order buys at the ask and sells at the bid, and a fast market can fill worse than the quote. Sales of US stocks also carry small regulatory fees. Enter 0 as the commission to see the cost that is left.

How do trading costs change expectancy?

Subtract the cost in R from the expectancy in R per trade. A system that averages +0.2R before costs and pays 0.13R per round trip keeps about +0.07R, roughly a third of its edge.

Why do costs matter more for short-term trading?

The cost per share is about the same whatever the holding period, but a short-term trade has a closer stop and a smaller target, so the same cost is a larger share of 1R and of the expected move. More trades per year multiply the total as well.

Is anything I enter saved?

No. The calculation runs in your browser; nothing is sent to Clear Tape or stored.

Related guides

Other calculators

From the calculation to the record

Save the entry, stop and target as a plan before the trade, then log the fills. The journal works out R, expectancy and drawdown from your own trades, and its AI score grades how closely each trade followed the plan. A free account is all it takes.