Portfolio Allocation Spreadsheet (How to Build One Step-by-Step)
- Compounding Investor
- 7 days ago
- 5 min read
Updated: 3 days ago
Most investors think they’re diversified because they own “a few different things.” But diversification isn’t the same as allocation control. Allocation is the part that stops one position, one sector, or one theme quietly taking over your portfolio.
When you don’t track allocation, you usually end up with:
Overexposure to a single stock/sector/theme
Imbalances that creep in over time (often without you noticing)
Poor decisions driven by emotion (adding to what’s already run up, ignoring what’s fallen behind)
A simple Excel allocation spreadsheet fixes this. It gives you one place to see what you own, what it’s worth, what percentage each holding represents, and whether you’re drifting away from your targets.
Allocation overview (how I plan my strategy)
This is what I use as the framework for managing allocation across my portfolio so I always know where I’m overweight or underweight.
What is portfolio allocation?
Portfolio allocation is simply the percentage of your total portfolio that’s invested in each asset (or bucket).
Example: if your portfolio is worth £100,000 and you have £12,000 in a global equity ETF, that ETF is 12% of your portfolio.
You can track allocation at different levels depending on how you invest:
By holding (each stock/ETF/fund)
By asset class (equities, bonds, cash, alternatives)
By sector or theme (tech, healthcare, energy, etc.)
By geography
For most DIY investors, the most useful starting point is: allocation by holding, plus a simple roll-up into a few buckets you actually rebalance. However, you can quickly get more sophisticated as can be seen in the system below and this is where you drive real strategic value and returns.
Why allocation matters (in real life)
Allocation is risk control. It’s the difference between “I like this stock” and “I’m willing to let this stock become 25% of my net worth.”
A good allocation process helps you:
Stay disciplined: you add based on targets, not headlines
Avoid emotional overexposure: winners don’t silently dominate your portfolio
Rebalance with confidence: you can see exactly what’s overweight/underweight
Make better decisions: you know the impact of every buy/sell before you place it
If you’ve ever looked at your portfolio and thought “I’m not sure what I’m actually exposed to,” this spreadsheet solves that in under an hour.
How to build a portfolio allocation spreadsheet in Excel (step-by-step)
You don’t need anything fancy. The goal is a simple table that calculates each holding’s value, its percentage of the portfolio, and the variance vs your target allocation.
Step 1) List your holdings
Create a table with these columns (starting in row 1):
Holding (name/ticker)
Units/Shares
Price
Value
Target %
Actual %
Variance (Actual % − Target %)
Tip from experience: keep the first version manual. You can automate prices later, but the logic matters more than the data feed.
Step 2) Calculate each holding’s value
In the Value column, multiply Units × Price.
Example formula (if Units is in B2 and Price is in C2):
=B2*C2
Copy it down for all holdings.
Step 3) Calculate total portfolio value
At the bottom of the Value column (or in a separate cell), sum the Value range.
Example:
=SUM(D2:D50)
Name this cell something like TotalValue (optional but helpful).
Step 4) Calculate each holding’s actual allocation %
Actual % is simply holding value ÷ total portfolio value.
Example (if Value is in D2 and total is in D51):
=D2/$D$51
Format the column as Percentage with 1–2 decimals.
Step 5) Add target allocations
In Target %, enter the allocation you want each holding (or bucket) to represent.
Keep it realistic. Targets are guardrails, not predictions. If you’re not sure, start with broad targets (e.g., core ETF 40%, satellite positions 5% each, cash 10%) and refine over time.
Step 6) Calculate variance vs target
Variance tells you what needs attention. It’s Actual % minus Target %.
Example (if Target % is E2 and Actual % is F2):
=F2-E2
Now you can instantly see what’s overweight (positive variance) and underweight (negative variance).
Allocation % + variance (what I actually use)
[IMAGE: allocation % + variance]
This is exactly how I track allocation and ensure my portfolio stays balanced.
Common mistakes (and how to avoid them)
Not tracking percentages (only £ values): percentages are what control risk.
No target allocation: without targets, you can’t tell drift from intention.
Letting drift compound over time: small drifts become big exposures after a strong run.
If you only take one thing from this post: track allocation monthly (or at least quarterly). The habit matters more than the perfect spreadsheet.
Without a system vs with a system
Without a system: you react to price moves, add to what feels good, and only notice concentration after it hurts.
With a system: you can see drift early, rebalance deliberately, and make buys/sells that move you toward your plan.
How this leads into a complete portfolio management system
Allocation is one piece of the bigger picture. A complete portfolio management system also tracks contributions, performance, and decision rules—so you’re not relying on memory or emotion.
If you want the full setup (allocation + tracking + performance + decision framework), that’s exactly what the Compounding Investor System is built for.
Who this is for
DIY investors who want a simple, repeatable process
Anyone building a long-term portfolio and trying to avoid concentration risk
Investors who want to rebalance logically instead of emotionally
Make this frictionless (so you actually use it)
Keep the spreadsheet to one page.
Update prices on a schedule (e.g., first weekend of the month).
Use conditional formatting on Variance (green underweight, red overweight).
Write down your target allocations once, then stop tinkering.
Next step
If you want the complete portfolio management system (including allocation, tracking, and performance), start here:
FAQ
How often should I update my allocation spreadsheet?
Monthly is a good default. Weekly is usually overkill unless you’re actively rebalancing or adding new money frequently.
Do I need target allocations for every single holding?
Not necessarily. Many investors set targets at the bucket level (core, satellite, cash) and then use position size limits for individual holdings.
What’s the simplest way to rebalance?
Use new contributions first: add money to what’s underweight. Only sell when drift is meaningful or when your risk has clearly changed.
Can I do this if I have multiple accounts (ISA, SIPP, brokerage)?
Yes. The key is to track allocation at the total-portfolio level, then optionally add a column for account so you can filter and sanity-check where each holding sits.
Internal links to add: Blog 2 (tracking), Blog 3 (CAGR), Blog 1 (system).
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