Most blown accounts are not blown by bad entries. They are blown by good entries in the wrong size. A trade that is right on direction but three times too large will still trip a drawdown or the Max Trade Loss rule the moment it moves against you.

Position sizing flips the order of operations. Instead of picking a contract count and hoping the stop survives, you decide what you are willing to lose, measure where you are wrong, and then calculate the largest size that keeps that loss inside your limit. The number of contracts is an output, not a choice.

One line does the whole job:

The piece that trips people up is stop ticks × tick value. That product is your risk per contract. Once you know what one contract loses at your stop, dividing your budget by it tells you how many you can hold.

Your dollar risk is a choice, but it has a hard ceiling. On Thunderbolt Classic and Vanguard the Max Trade Loss is 1.5% of account size on any single open trade. On Thunderbolt Legacy the ceiling is higher, 2% of account size. Exceeding it triggers an automatic breach that terminates the account, even if you are overall in profit. It applies on both the challenge and the funded phase.

So 1.5% (2% on Legacy) is the most any one trade may risk. Here is that dollar cap by account size:

The cap is a ceiling, not a target. Sizing to the full 1.5% means one losing trade spends your entire single-trade allowance and takes a large bite out of your daily drawdown. Many traders set their working risk lower, at 0.5% or 1% ($250 or $500 on a $50K account), and keep 1.5% as the line they never cross. Whatever number you pick becomes the "Dollar risk" in the formula. 1.5% is the wall.

On Legacy: swap in the 2% ceiling ($1,000 on $50K, $2,000 on $100K). The worked examples below use the 1.5% cap of Thunderbolt Classic and Vanguard.

Your stop is where the trade is wrong. Measure the distance from your entry to that stop, then convert it to ticks:

Stop ticks = (Entry price minus Stop price) / Tick size.

Example: you buy ES at 5,000.00 and your stop sits at 4,994.00. That is a 6-point move. ES has a 0.25 tick size, so 6 / 0.25 = 24 ticks. For CL (Light Sweet Crude Oil) with a 0.01 tick size, a stop 0.30 away is 0.30 / 0.01 = 30 ticks. Every instrument has its own tick size and tick value, listed in Tick size and tick value explained.

Multiply stop ticks by tick value to get your risk per contract, then divide your dollar risk by it. The rounding direction matters:

Always round the contract count down. If the math gives 2.5 contracts, you trade 2, not 3. Rounding up would push the trade over your budget, and if the budget was the 1.5% cap, rounding up would breach it. Rounding down keeps you safely inside the limit and leaves a small buffer for slippage on the stop.

You want to trade ES with a 24-tick stop (6 points). Risk per contract = 24 × $12.50 = $300.

On the $50K account the raw answer is 2.5, so you round down to 2 ES and risk $600. On the $100K account it lands exactly on 5 ES for the full $1,500. Notice the $50K trader cannot use the whole budget with ES: 2 contracts risk $600 and a third would risk $900, over the cap. That leftover $150 is the coarseness of full-size contracts on a small account, and it is exactly the problem micros solve.

MES (Micro E-mini S&P 500) is one tenth the size of ES. Same chart, same 24-tick stop, but risk per contract = 24 × $1.25 = $30.

Because each MES risks only $30 at this stop, the $50K trader can fill the budget exactly: 25 MES risk $750, right at the cap, with nothing left on the table. 25 MES is 2.5 ES worth of exposure, the exact size the ES trader could not hold. That is the point of micros: they cut the risk-per-contract by ten, so you can dial size in fine steps instead of jumping in $300 blocks.

This matters most on smaller accounts. The smaller your dollar budget, the more a full-size contract forces you to either overshoot the cap or waste room. Micros give a $50K (or smaller) account the same fine control a large account gets from full-size contracts. See Mini vs micro contracts for the full list of the 13 micro-sized contracts.

You want to trade CL (Light Sweet Crude Oil) with a 30-tick stop (0.30 in price). Risk per contract = 30 × $10.00 = $300.

Same coarseness as ES on the $50K account: 2.5 rounds down to 2 CL. Crude has a micro, MCL (Micro WTI Crude Oil), with a $1.00 tick value. Switching to MCL at the same 30-tick stop makes each contract risk 30 × $1.00 = $30, so the $50K trader could hold 25 MCL for the full $750 instead of leaving $150 unused.

MGC (Micro Gold) is one tenth of GC (Gold). You want a 50-tick stop (5.0 in price, since MGC and GC both have a 0.1 tick size). Risk per contract = 50 × $1.00 = $50.

The full-size GC has a $10.00 tick value, so at the same 50-tick stop one GC risks $500. On the $50K account that is only 1 GC (750 / 500 = 1.5, rounded down), using $500 of the $750 budget. MGC lets the same trader hold 15 micros for the full $750, or 5 micros for a tighter $250 (0.5%) budget. Fine steps, exact control.

The pattern across all four examples is the same. A full-size contract moves your risk in large blocks: $300 at a time for ES and CL at those stops, $500 for GC. On a $50K account with a $750 budget, that coarseness forces you to either overshoot the cap or leave money on the table.

A micro cuts the block size by ten (or by five, fifty, or five hundred for a few contracts). Suddenly your budget divides cleanly and you can size right up to your chosen risk without crossing it. That is why micros are the practical choice for precise sizing on $50K accounts and smaller, and why they are worth learning even if you plan to trade full-size later.

Rounding up. 2.5 contracts means 2, not 3. Rounding up breaks the budget and can breach the 1.5% cap.

Sizing first, stop second. Picking "I will trade 3 ES" and then placing a stop wherever it looks nice is how the Max Trade Loss rule gets tripped. Stop first, size second.

Treating 1.5% as the target. It is the ceiling. Repeatedly risking the full 1.5% means a short losing streak does real damage and eats your daily drawdown fast.

Splitting to dodge the cap. Positions in the same instrument and the same direction are counted as one trade, so you cannot split an oversized position across two tickets. See Max single trade loss.

The whole method in one block:

Contracts = Dollar risk / (Stop ticks × Tick value)

Need the tick value for a specific contract? Read Tick size and tick value explained.

Want the full detail on the 1.5% cap and how a breach works? Read Max single trade loss.

Deciding between full-size and micro contracts? Read Mini vs micro contracts.