Sending the same lot size to a 25k account and a 200k account isn’t copying — it’s risking eight times as much on the small one and hoping nobody notices. The whole discipline of multi-account copying is copying the risk, not the lots.
When one strategy runs across several funded accounts, the signal is identical everywhere: same entry, same stop, same direction. The only thing that should change from account to account is position size, and getting that mapping right is the entire game. Do it well and every account experiences the trade as the same slice of its own balance. Do it wrong and your smallest account quietly carries your largest risk.
Why fixed-lot copying is the classic mistake
The obvious default is to send the same number of lots to every account. It’s simple, it’s fast, and it’s wrong.
One lot on a 25k account is a completely different bet than one lot on a 200k account. The dollar risk is the same, but the percentage of the account at stake is eight times higher on the small one. So the account with the least drawdown headroom absorbs the most damage on every loser and is the first to breach — the exact opposite of what you want.
Fixed lots also wreck your ability to read performance. When you review results, the small account’s equity swings dwarf the big one’s, and you can’t tell whether the strategy is working or whether one account is simply oversized. The unit that makes trades comparable across accounts is the R-multiple — risk-normalised profit and loss — and fixed lots destroy it. If you aren’t already thinking in R, this primer on R-multiples is the foundation everything below rests on.
Balance-proportional vs risk-proportional scaling
There are two honest ways to scale, and they answer different questions.
- Balance-proportional sizing sets each account’s lots in proportion to its balance. A 100k account trades twice the lots of a 50k account. Simple, and it keeps dollar risk roughly in line with account size.
- Risk-proportional sizing sets each account’s lots so the stop-loss distance costs the same percentage of every account. This is the one you actually want. It respects the fact that the stop is fixed in price terms while each account has a different balance to measure that loss against.
Balance-proportional is a decent shortcut when every account shares the same instrument, stop distance, and rule set. Risk-proportional is the correct answer the moment any of those differ. A lot size calculator turns a target risk percentage and a stop distance into the exact lots for each balance — which is precisely the mapping a copier should apply automatically, once per account, on every trade.
Handling different account sizes (25k vs 200k)
The practical wrinkle is that prop accounts come in fixed tiers, and you often run several tiers at once.
Anchor everything to one number: risk per trade as a percentage of each account’s balance. Choose the percentage once, then let the size fall out of it. The 25k account trades a small fraction of a lot; the 200k trades several. Both feel the trade identically as a share of themselves.
Two things bite at the extremes:
- Minimum lot size. On the smallest account, your calculated size may round below the platform’s minimum. When that happens, the account either sits out the trade or accepts slightly more risk than its siblings — decide which, deliberately, instead of letting rounding decide for you.
- Instrument granularity. Futures trade in whole contracts, so a small account can’t take a fractional position. Risk-proportional math might say 1.4 contracts; you can trade 1 or 2, and neither is exactly your target. Round toward less risk when unsure. A position size calculator that respects the instrument’s minimum increment keeps you honest here.
Adjusting for different drawdown floors
Balance is only half the picture. Two accounts with identical balances can have very different loss capacity depending on the firm’s drawdown model.
An account on a static drawdown has a fixed floor — you know exactly how much you can lose before a breach. An account on a trailing drawdown ratchets its floor up as you profit, so your true headroom depends on your high-water mark, not your starting balance. Copying identical risk to both ignores that the trailing account may have far less room left after a good run.
The safer rule: size each account against its current distance to breach, not its nominal balance. When an account has run up and its trailing floor has followed, its real cushion can be thinner than a same-balance static account sitting flat. Firms define the floor in their own way — MyFundedFutures and others each set it differently — so confirm the model with your firm and treat drawdown headroom, not balance, as the thing you’re really scaling against.
A worked example across three accounts
Say you run three accounts and take one setup with a fixed stop distance, and you’ve decided each account risks the same percentage of its balance.
| Account | Balance | Drawdown type | Sizing basis |
|---|---|---|---|
| A | 25k | Static | Full % of balance — clean, known headroom |
| B | 100k | Static | Full % of balance — 4× account A’s lots |
| C | 100k | Trailing, up on the run | % of remaining headroom, not balance |
Accounts A and B size straight off balance because their floors are fixed and their cushions are known. Account C shares B’s balance but has run into its trailing drawdown, so its real distance-to-breach is smaller — you size it down to match the headroom it actually has, not the balance it displays. The signal is identical on all three; the lots are not. That’s the point: one decision, three sizes, equal risk relative to what each account can afford to lose.
A copier that applies this mapping per account — and holds a hard limit at the broker so no account can exceed its share even during a fast fill — turns daily mental arithmetic into a rule you set once. The math is the easy part. Executing it correctly on every trade, on every account, without a single slip is what actually protects the funded accounts.
Related: Lot size calculator · R-multiple explained · Position size calculator