Dynamic Position Sizing: Adjusting to Volatility

Right. Let me tell you something I learned the hard way—and I mean the genuinely catastrophic way—back in 2015 during the Swiss franc unpegging.

I was sitting in my office on Bishopsgate, convinced I was an absolute genius. Three years of profitable trading under my belt, a Range Rover in the car park that I absolutely did not need, and the sort of arrogance that only comes from getting lucky during a bull run. I was trading fixed position sizes like some sort of caveman. One lot, always one lot. The market could be doing 5 pips of volatility or 150 pips of volatility—didn’t matter. One lot, every single time.

Then January 15th, 2015 happened.

The Swiss National Bank removed the EUR/CHF floor, and the pair moved something like 3,000 pips in about 20 minutes. My stop loss? Didn’t exist at that price level anymore. My account? Vaporised faster than a can of Red Stripe in a London heatwave.

That’s when I learned the most valuable lesson of my trading career: fixed position sizing is for people who enjoy financial ruin.

The Problem With Being Predictable (And Stupid)

Here’s what kills most retail traders—and I’ve watched hundreds of them, mate. They treat their trading like it’s some sort of automated factory line. Same lot size, same leverage, same blissful ignorance, day after day. They see a trade setup they like, and they hit the buy button with the same mechanical consistency of a robot with absolutely no survival instincts.

The market doesn’t care about your routine. It doesn’t give a toss about your system or your edge or your YouTube-certified trading certificate. What it does care about is volatility. And volatility is a sneaky bastard that changes every single day.

On a calm Tuesday morning, when the data is light and the spreads are tight, you might have 50 pips of breathing room before you hit your stop loss. Three days later, when there’s a major economic announcement or a central bank decision looming, that same currency pair might move 150 pips in a single candle.

If you’re using the same position size in both scenarios, you’re not managing risk—you’re playing Russian roulette with extra bullets.

What Dynamic Position Sizing Actually Means

Let me cut through the consultant-speak bullshit. Dynamic position sizing simply means: adjust your lot size based on current market conditions.

It’s elegant. It’s simple. It’s absolutely revolutionary if you’ve been trained by some YouTube charlatan who thinks position sizing is “something that happens automatically.”

The concept works like this:

High volatility = smaller position size Low volatility = larger position size

This keeps your actual risk (in pounds, euros, dollars—whatever currency you haven’t blown on trying to become a day trader) relatively constant across different market conditions.

Instead of risking the same amount on every trade regardless of circumstances, you’re maintaining something closer to a consistent risk profile. On a choppy day when the market’s moving about like it’s had seventeen espressos, you trade smaller. On a calm day when price action is smooth and predictable, you can afford to trade slightly larger.

Revolutionary? No. Common sense? Absolutely. Practised by actual professionals? You’d be shocked how many don’t.

The Maths Bit (Don’t Worry, It’s Not Complicated)

Most professional traders use something called ATR (Average True Range) as their volatility measurement. It’s not magic—it’s just a technical indicator that measures how much an instrument typically moves over a given period.

Here’s the formula that’ll change your life (or at least your bank account):

Position Size = (Account Risk in Pips / Current ATR) × Base Lot Size

Let’s say you’re risking 50 pips per trade on a £10,000 account. The EUR/USD ATR is currently 45 pips. Your calculation looks like:

(50 / 45) × 0.1 lots = ~0.11 lots

Simple. Effective. Boring. Which is exactly what you want in risk management.

When volatility spikes—say the ATR jumps to 120 pips during a major news event—your position size automatically shrinks:

(50 / 120) × 0.1 lots = ~0.04 lots

You’re trading smaller when the chaos is larger. You’re protecting your capital when it matters most.

Why Most Traders Still Get This Wrong

I’ve mentored enough people to know that understanding dynamic position sizing and actually implementing it are two entirely different animals.

The problem is psychological, innit. When volatility is low and everything feels safe, traders get cocky. “The market’s calm, I’ll take a slightly larger position.” Then volatility spikes, stops get hit wider, and suddenly they’re furious at the market instead of furious at themselves for ignoring their own risk management system.

Then there’s the opposite problem: traders who get too cute with their calculations. They’ll use seventeen different volatility indicators, overlay them with Fibonacci sequences, and create some sort of overcomplicated position-sizing algorithm that changes three times per day. By the time they’ve calculated whether they should trade 0.08 or 0.09 lots, the trade’s already moved 50 pips in the wrong direction.

Keep it simple. Use ATR. Adjust your lot size. Move on with your life.

The Real Edge

Here’s something that’ll hurt your ego: position sizing won’t make you more money. It’ll make you less likely to lose everything.

That’s the entire game, mate. I’ve known traders with mediocre systems who made millions because they had bulletproof risk management. I’ve also seen traders with genuinely good setups blow themselves up because they couldn’t resist the urge to over-leverage during volatile periods.

Dynamic position sizing is unglamorous. It doesn’t make for exciting Twitter content. You won’t get swarmed by Instagram followers for telling them that you reduced your lot size by 30% because volatility increased. But you’ll still have a trading account in five years, which is more than I can say for 90% of retail traders.

The Bottom Line

Use dynamic position sizing. Measure volatility with ATR or whatever metric you prefer. Adjust your position size accordingly. Don’t be a muppet about it. Don’t over-engineer it.

And whatever you do, don’t be like me in 2015—convinced that the laws of probability don’t apply to you personally.

They do.

Now go calculate your positions properly.