Metrics explained
Eight numbers, explained honestly.
Every figure on this site is plain arithmetic on values you typed. This page shows the formula behind each one, a small worked example with made-up numbers, and what the figure cannot tell you. Read it once and the dashboard stops being a black box.
Education about arithmetic. Not investment advice.
Market value
quantity × price now
What a position is worth at the price you typed. The dashboard adds these up for the total. If a price is stale, the value is stale with it.
Illustrative example 12 units at 40.00 is worth 480.00.
Cost basis
sum of quantity × cost per unit
What you paid in total for what you hold now. If you bought in stages, enter one blended cost per unit. This tool does not track individual tax lots.
Illustrative example 10 units at 20 plus 5 units at 30 cost 350 for 15 units, an average of 23.33 each.
Unrealized profit or loss
market value − cost basis
The gain or loss on paper if you still hold the position. It becomes realized only when you sell, and taxes, fees and dividends are not included here.
Illustrative example Those 15 units priced at 26 are worth 390. Against a basis of 350 that is +40, or +11.4%.
Weight
position value ÷ total value
How much of the portfolio rides on one position. Weights always add to 100%, so a rising position raises its own weight and lowers everyone else’s.
Illustrative example Positions worth 480, 320 and 200 total 1,000 and weigh 48%, 32% and 20%.
Concentration
effective positions = 1 ÷ (sum of weight squared)
Counting holdings can mislead, since ten positions with one giant among them behave like fewer. Effective positions treats unequal weights fairly. The concentration index is the same sum scaled to 10,000.
Illustrative example Weights of 48%, 32% and 20% give 0.2304 + 0.1024 + 0.04 = 0.3728. That is 2.68 effective positions and an index of 3,728. Four equal positions give exactly 4.0.
Rebalance trade
(target weight × (total + cash)) − current value
Divide the result by the price to get units. A positive number means buy, a negative number means sell. It is a mechanical gap, not a view on whether the target is wise.
Illustrative example A 480 position in a 1,000 portfolio with a 40% target should be 400. The gap is −80, which is 2 units at 40.
Scenario shift
new value = value × (1 + shift)
A stress test multiplies every position by the move you choose. It ignores timing, correlation and what you might do in response, so treat it as a ruler, not a crystal ball.
Illustrative example A 480 position shifted by −20% becomes 384.
Recovery
rise needed = 1 ÷ (1 − fall) − 1
A fall shrinks the base that the next move applies to, so getting back costs a larger percentage than the drop. The gap widens quickly as falls get deeper.
Illustrative example 480 falls 20% to 384. Returning to 480 needs +25%, since 384 × 1.25 = 480.
Honest limits
What it cannot do
- It has no market data, so it can never tell you a price.
- It does not know your taxes, fees, dividends or currency exposure.
- It does not track tax lots, options, leverage or short positions.
- It cannot say what you should buy, hold or sell.
Live
Your numbers
No holdings to read
This panel mirrors the holdings stored in your browser. Add positions on the dashboard and the figures from this page appear here, computed for you.
- Positions counted
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- Total value
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- Unrealized P/L
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- Largest weight
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- Effective positions
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- Concentration index
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- Out of 10,000
Glossary
Words you will meet
- Position
- One holding: a symbol, how many units you own, what you paid and what it is priced at now.
- Unrealized
- A gain or loss that exists only on paper because you still hold the asset.
- Realized
- A gain or loss locked in by selling. This tool does not calculate realized results.
- Drawdown
- The fall from a previous high to a later low, usually quoted as a percentage of the high.
- Rebalance
- Trading back toward chosen weights after price moves have pushed them off course.
- Basis
- The amount you paid, used as the reference point for profit and loss.
Questions
Edge cases, answered
What happens if I leave cost blank?
The position still counts toward value and weight, but it is left out of cost basis and profit and loss. The dashboard tells you how many positions are missing a cost so the totals are never silently wrong.
Why are negative numbers rejected?
The maths here assumes you own units outright. A negative quantity would imply shorting or borrowing, which changes risk in ways a simple scratchpad cannot represent honestly.
Why might my rebalance plan not reach the target exactly?
With whole units only, trades are rounded, so weights land close to target rather than on it. Fractional units give the exact answer where your broker allows them.
Where is my data stored?
In your browser’s local storage on this device. If storage is blocked, the page keeps your entries in memory until you close it and says so on the dashboard.