Fund Size Calculator
The formula
What the fund sizing tells you
A fund is its strategy priced: deal count × check × reserves, divided by the investable share left after fees — the equation that should cap everyone's ambitions.
Calculation: Equity needed = deals × check × (1 + reserves); fund = equity ÷ investable %. Enter your inputs and every substitution is shown below the result.
Reading the result
The concentration line tells the story: a $100M fund writing $6M checks holds ~16 names with reserves; below twenty positions, venture diversification stops working.
Rules of thumb: Seed funds $30–80M; Series A funds $100–300M; checks 1–4% of fund
Limitations and best practice
The classic failure is oversized relative to entry opportunity: a $150M fund on a $40M strategy buys index-like stakes at private-market illiquidity.
This calculator gives an estimate based on standard formulas; it is not professional financial, medical, legal or engineering advice. Verify anything you plan to act on with a qualified professional and your own records.
Frequently asked questions
What is the investable ratio?
Do reserves really matter?
Source & methodology
Standard fund planning practice.
Fund Size: what this tool answers
This page was written for one job: turning your own inputs into a defensible figure, with the working shown. Fund Size is the kind of number people argue about from memory. This page ends that argument with arithmetic you can watch happen: enter your figures, get Recommended fund size in real time, and see every substitution printed below.
It helps to separate the mechanics from the interpretation. The mechanics are fixed: Equity needed = deals × check × (1 + reserves); fund = equity ÷ investable %. Anyone, anywhere, entering the same inputs will get the same $108,235,294. The interpretation is where experience counts: whether $108,235,294 is good, normal or alarming depends on comparisons covered below, and that is the part most articles about Fund Size never explain.
People rarely disagree about arithmetic; they disagree about assumptions that were never written down. Printing the substitution and the sensitivity ranking removes that category of disagreement for Fund Size.
Every figure in the prose is generated by the engine rather than written beside it — the worked example resolves to recommended fund size = $108,235,294 on the default inputs, and the sensitivity section ranks the inputs that move the result — Investable share of commitments first, at ≈11.1 % of the headline for a ten-percent error either way in that input. Read the sections in order and you will be able to reproduce every figure by hand.
Every input in Fund Size, and what it does to the answer
The engine implements a single stated model: Equity needed = deals × check × (1 + reserves); fund = equity ÷ investable %. There is no hidden coefficient and no login-gated precision — the formula printed is the formula executed, which is also what makes the result citable.
Portfolio companies planned (example value 23) is a plain measured quantity — the unit shown in the label is the unit the formula expects. Replace the example with the figure from your own records — the tool recomputes instantly and the printed steps follow your numbers.
Average first check ($) (example value 2,500,000) is a numeric input whose unit is fixed by the label; a wrong unit is a wrong answer wearing a plausible disguise. The example value is there to demonstrate the mechanics, not to describe your situation — overwrite it.
Reserve ratio for follow-ons (%) (example value 60) is a quantity rather than a category — precision here is cheap and worth having. Enter it exactly as your document states it — quoted annual, monthly and effective rates are three different numbers.
Investable share of commitments (%) (example value 85) is a numeric input whose unit is fixed by the label; a wrong unit is a wrong answer wearing a plausible disguise. Enter it exactly as your document states it — quoted annual, monthly and effective rates are three different numbers.
The default Fund Size calculation, written out in full
Abstract formulas are hard to trust, so here is the complete substitution using the default inputs, written the way an examiner would want it. Starting figures: Portfolio companies planned, Average first check ($), Reserve ratio for follow-ons (%), Investable share of commitments (%). Run to the end, the recommended fund size resolves to $108,235,294 — Deploys $92,000,000 across 23 companies; 15% of commitments goes to fees and overhead on the bands this tool uses.
- Equity = 23 × $2,500,000 × (1 + 60%) = $92,000,000
- Fund = ÷ 85% = $108,235,294
Total equity including reserves — $92,000,000. If your inputs change, this is usually the first companion figure to move.
First check as % of fund — 2.31 %. Compare it against the main result of $108,235,294 before drawing conclusions.
Average ownership needed for a 3× at $300M exit — 2.50 %. Compare it against the main result of $108,235,294 before drawing conclusions.
Re-running with your own figures is instant; re-running by hand once is the best way to know the tool is telling you the truth.
How far Fund Size can reasonably move
Single-point answers invite false confidence, so the same engine was run across a band around the input that matters most here. Each row is a full recalculation of Fund Size, not an interpolation.
| Investable share of commitments setting | Recommended fund size |
|---|---|
| 80 % of the example value | $135,294,118 |
| 90 % of the example value | $120,261,438 |
| example inputs | $108,235,294 |
| 110 % of the example value | $98,395,722 |
| 120 % of the example value | $90,196,078 |
That spread — $90,196,078 at the low end, $135,294,118 at the high — is what a careful read of Fund Size looks like: a band you can state out loud, with the reason for each edge. Reproduce it in the form above by editing Investable share of commitments alone; the substitution steps will follow your figures exactly.
Sensitivity: which inputs change Fund Size the most
Generic advice says “it depends on your inputs”; this section says exactly how much. Each field was perturbed by ±10 % in isolation and the recommended fund size recomputed, so the ranking below is measured rather than asserted. For Fund Size the ranking is measured rather than guessed, and it belongs to these defaults: shift the starting point and the order can shift with it.
- Nudge Investable share of commitments by ±10 % and Fund Size lands between $98,395,722 and $120,261,438 (sensitivity ≈11.1 %)
- Portfolio companies planned +10 % → Fund Size = $119,058,824 · −10 % → $97,411,765 (the recommended fund size shifts ≈10.0 %)
- Nudge Average first check by ±10 % and Fund Size lands between $97,411,765 and $119,058,824 (sensitivity ≈10.0 %)
- Reserve ratio for follow-ons: ten percent up gives $112,294,118, ten percent down gives $104,176,471 — ≈3.8 % of the recommended fund size either way
Investable share of commitments is the dominant lever here: ten percent either way moves the result by about 11.1 %, from $98,395,722 to $120,261,438. That is where a careless figure does the most damage, so check it against a source, and treat Portfolio companies planned as the second priority (≈10.0 % per ten percent). Everything below that can stay approximate, which is a licence to stop chasing data that would not change the decision.
Interpreting the Fund Size verdict
Nobody acts on a bare figure — they act on a figure with a comparison attached. On the example inputs the band reads “Deploys $92,000,000 across 23 companies; 15% of commitments goes to fees and overhead”; your own figures place you on a different rung of the same ladder. How much of that band is luck? On Investable share of commitments alone ten percent either way covers $98,395,722 to $120,261,438. The practical reading rules: compare against your own history before comparing against other people; treat band boundaries as zones, not walls — one point on the wrong side of a threshold rarely changes a real outcome; and when a companion output contradicts the headline, believe the pair.
Placing this figure in context: calculators of this kind differ less in arithmetic than in what they choose to ignore. This one keeps Portfolio companies planned explicit so that the omissions are visible rather than hidden in a preset.
Why Fund Size results go wrong — and how to prevent it
The classic failure is oversized relative to entry opportunity: a $150M fund on a $40M strategy buys index-like stakes at private-market illiquidity. This calculator gives an estimate based on standard formulas; it is not professional financial, medical, legal or engineering advice. Verify anything you plan to act on with a qualified professional and your own records.
Stopping at the first plausible answer. If the result surprises you, the productive question is which input would have to be wrong for the surprise to disappear — then go check that input.
This model has its own particular trap: Investable share of commitments carries ≈11.1 % of the response per ten percent of error, so effort spent elsewhere is largely decorative.
A final trap is presentation: reporting Fund Size to more decimal places than the inputs support. The tool prints what the arithmetic gives; you should quote only what your least precise field justifies.
A quick check for any Fund Size figure
- Compare the result with one independent method or published benchmark.
- Check that every field the formula needs actually arrived from a document, not from recollection.
- Check Investable share of commitments before anything else: it is the measured dominant input, ≈11.1 % of Fund Size per ten percent.
- Verify each input against its original source document, not memory.
- Note the date and the inputs beside the number so the figure can be audited later.
- Run the ±10 % stress on the top two levers and check that your conclusion survives both.
Step by step: getting a trustworthy Fund Size out of this tool
Using a calculator well sounds trivial, but the difference between a decision-grade figure and a throwaway one lives entirely in the routine. The routine for Fund Size takes a minute to learn and applies to every input above.
Step 1 — one document, one pass. Open the statement, label or record that holds portfolio companies planned, average first check ($), reserve ratio for follow-ons (%), investable share of commitments (%) and transcribe straight into the form. Transcription from a single source removes the mismatch errors that appear when figures are assembled from three different places. Precision is a promise you make about your data; make sure your inputs can keep it.
Step 2 — baseline before exploration. Get one defensible Recommended fund size on screen before you start nudging numbers. Without a baseline, every variation looks interesting and none of them means anything. Rounding early is the quietest way to introduce a permanent error.
Step 3 — change one input at a time. Nudge a single field by ten percent, watch the headline and its companions move, then undo it. Two or three fields will dominate — the sensitivity table above already ranks them for this engine. Numbers are cheap to produce and expensive to retract; the extra minute is the cheapest insurance available.
Step 4 — stress before you commit. A decision that survives a ten-percent squeeze on its two biggest inputs needs no luck to be sound. One that does not survive is a decision about hope, not about arithmetic. A figure nobody can reproduce is a figure nobody will act on twice.
Step 5 — save the story with the figure. A number without its inputs and its date is unusable within a quarter. Record $108,235,294, the assumptions behind it, and today’s date; your future self will be auditing a stranger’s arithmetic. Half of a good calculation is knowing which input you would hate to be wrong about.
From calculation to decision: where Fund Size earns its keep
In Startup Metrics the figure computed here is usually the first one somebody asks to see. Having it — with the formula behind it — changes your position in the conversation from participant to reference. Write the figure down before moving on; memory flatters whichever number you saw last.
Used properly this is a five-minute filter that saves weeks. Compute Fund Size, reject what fails, and only then bring in the expensive analysis for the survivors. A calculation you cannot explain to somebody else is a calculation you cannot defend.
Treat Fund Size like a smoke alarm rather than a painting — its value is in being tested periodically, not in being admired once. Repeating a calculation with the same numbers proves only that the arithmetic is reliable — which is worth knowing.
Quick answers: what searchers ask about Fund Size
What affects Fund Size the most?
Fund Size is driven above all by Investable share of commitments. Perturbing only that field by ten percent either way produced $98,395,722 against the $108,235,294 baseline — a ≈11.1 % response, while Portfolio companies planned manages ≈10.0 %.
Which matters more: portfolio companies planned or investable share of commitments?
For Fund Size, Investable share of commitments wins the head-to-head (≈11.1 % against ≈10.0 % per ten-percent change). Knowing which input dominates is the difference between careful work and merely slow work.
What is a typical Fund Size?
On the worked example above Fund Size comes out at $108,235,294. Treat that as one point on a distribution rather than a norm: the bands, the companion outputs and the sensitivity ranking tell you how wide the plausible range really is.
How do I calculate Fund Size by hand?
Three steps: write the formula (Equity needed = deals × check × (1 + reserves); fund = equity ÷ investable %), insert your values, and simplify. The worked example section shows exactly that chain for the default inputs; replicating it once on paper teaches you more about Fund Size than any number of calculator runs.
What happens to Fund Size if investable share of commitments changes by 10 %?
The engine was re-run with that field moved by ten percent while everything else stayed fixed: the recommended fund size goes across $98,395,722 to $120,261,438, a swing of roughly 11.1 % around the $108,235,294 baseline. That ratio is the practical definition of how much this input matters.
Is the Fund Size result of $108,235,294 good or bad?
Neither, on its own — the label “Deploys $92,000,000 across 23 companies; 15% of commitments goes to fees and overhead” is the band this figure falls in for the example inputs, and your own inputs will place you elsewhere on the same ladder. Judge the number against your history and your alternatives, and remember that a ten-percent error in Investable share of commitments alone moves it by ≈11.1 %.
How often should I check Fund Size?
Whenever an input changes by more than a few percent, and otherwise on the rhythm of your decisions — before a purchase, a review, a renewal. Fund Size is a snapshot, not a subscription; stale snapshots are the most common silent error in Business & Entrepreneurship planning.
Should I use Fund Size before launching?
Yes — a Fund Size run on honest inputs before spending is the cheapest consulting an entrepreneur can buy. Re-run at every pricing change; the number moves more often than founders expect.
What is the investable ratio?
Commitments minus fees and expenses — commonly 80–90% for venture.
Do reserves really matter?
Follow-ons on the winners are where funds compound; thin reserves convert winners into diluted spectators.
Is my data private on this page?
Yes — computation happens locally in your browser, with no account, no tracking of your inputs and nothing sent to a server. The printed formula is the whole story of what happens to your figures.
Glossary for Fund Size
- Total equity including reserves
- $92,000,000 for the Fund Size worked case; it sits next to the main result because it carries context the headline leaves out.
- First check as % of fund
- 2.31 % for the Fund Size worked case; it sits next to the main result because it carries context the headline leaves out.
- Average ownership needed for a 3× at $300M exit
- 2.50 % for the Fund Size worked case; it sits next to the main result because it carries context the headline leaves out.
- Recommended fund size
- The primary output of this tool: $108,235,294 for the default inputs, computed exactly from Equity needed = deals × check × (1 + reserves); fund = equity ÷ investable %.
- Worked example
- Every substitution in order, from the example inputs to $108,235,294 — the audit trail for the headline figure.
- Verdict band
- The interpretation attached to a result (“Deploys $92,000,000 across 23 companies; 15% of commitments goes to fees and overhead” on these inputs), which turns a bare number into a position on a scale.
- Sensitivity (±10 %)
- How far the Fund Size moves when a single input is nudged ten percent either way; the ranked list on this page is computed live from this engine.
Methodology, sources and limits
Everything above runs on one stated formula, applied without hidden coefficients: Equity needed = deals × check × (1 + reserves); fund = equity ÷ investable %. Source of record: Standard fund planning practice. Any other implementation of this model should return the same figure for the same inputs. If one does not, the difference is in its assumptions — which this page prints and that one probably does not.
Nothing here replaces a qualified professional, and nothing here is approximate either — the arithmetic is exact, and the honesty is in the inputs you supply. The promise to the reader is narrow and testable: same inputs, same output, no silent rounding, and no figure presented without the formula that produced it.
Turning this Fund Size into a decision
Save the number together with its inputs and today’s date; a Fund Size figure without context is unusable the moment an input changes.
This page was written for people who need one trustworthy number before their next decision, and the promise is that nothing above required trust. Bookmark the tool, re-run it whenever an input moves by more than a few percent, and keep the date with the number.