PEG Ratio Calculator
The formula
What the peg ratio tells you
The size and shape of the move between two figures — total percent, absolute delta and the annualised rate — for peg ratio.
Calculation: change % = (after − before) ÷ before × 100; annualised = (after ÷ before)^(1/periods) − 1. Enter your inputs and every substitution is shown below the result.
Reading the result
Compare the annualised line with the same measure from a rival or a baseline; the raw percent flatters long periods and punishes short ones.
Limitations and best practice
Percentage-point vs percent confusion: a move from 4 % to 6 % is +50 % relatively but +2 points — state which you mean.
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
Is percent change symmetric?
Why annualise?
Source & methodology
Standard growth arithmetic.
PEG Ratio: the number, the method and the caveats
You are here because you need a specific number, and you want to see how it was produced before you rely on it. There are plenty of pages about PEG Ratio; almost none of them show the working. This one does: the formula, every input, a fully computed example, and a sensitivity analysis calculated live from this engine’s own defaults.
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 PEG Ratio.
A calculation like this one is worth roughly as much as a careful sentence: it forces several vague considerations into one comparable quantity. Once PEG Ratio is on the table, the argument can stop being about impressions.
Every figure in the prose is generated by the engine rather than written beside it — the worked example resolves to PEG Ratio = 23.47% on the default inputs, and the sensitivity section ranks the inputs that move the result — Before first, at ≈58.5 % of the headline for a ten-percent error either way in that input. Work down the page and by the end you could re-derive the result in a spreadsheet from memory.
The PEG Ratio formula, explained
Here is the complete model this tool runs — change % = (after − before) ÷ before × 100; annualised = (after ÷ before)^(1/periods) − 1 — with each input explained below. If a competitor’s page gives you a different answer from the same inputs, this is the text that settles which of you is right.
Before (example value 98) is a quantity rather than a category — precision here is cheap and worth having. This input feeds the formula directly; a defensible figure here is worth more than false precision anywhere else.
After (example value 121) is a quantity rather than a category — precision here is cheap and worth having. If you are unsure what belongs in this field, look at the printed steps: the substitution shows exactly how the engine uses it.
Periods between (years) (example value 6) is a quantity rather than a category — precision here is cheap and worth having. If the period is partial, decide whether you mean elapsed or planned time and keep that meaning across every field.
The default PEG Ratio calculation, written out in full
The tool prints its own working; this is the same arithmetic on the example values, reproduced so you can follow it by hand. Starting figures: Before, After, Periods between (years). The endpoint of that chain is 23.47% of PEG Ratio, sitting in the “Solid growth” band.
- Δ = 121.00 − 98.00 = 23.00
- Percent = 23.00 ÷ 98.00 × 100 = 23.47 %
- Annualised = (121.00 ÷ 98.00)^(1/6.0) − 1 = 3.58 %
Absolute change — 23.00. This is the number experienced users quote when the headline alone would mislead.
Per-period (annualised) — 3.58%. This is the number experienced users quote when the headline alone would mislead.
Multiple — 1.23 ×. Read next to the headline, this is the figure that shows the shape of the trade-off.
Keep this worked example open while you enter your own figures: matching the shape of the substitution is the fastest way to spot a unit or convention mistake.
Scenario table: PEG Ratio at ±10 % and ±20 % of the key input
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 PEG Ratio, not an interpolation.
| Before setting | PEG Ratio |
|---|---|
| 80 % of the example value | 54.34% |
| 90 % of the example value | 37.19% |
| example inputs | 23.47% |
| 110 % of the example value | 12.24% |
| 120 % of the example value | 2.89% |
Across 5 settings of Before, the result spans 2.89% to 54.34%. A decision that only works at one row of this table is a decision waiting for an input to move. Reproduce it in the form above by editing Before alone; the substitution steps will follow your figures exactly.
Where PEG Ratio is fragile — and where it is not
Nobody should have to guess which input matters. The engine was re-run once per field below — ten percent up, ten percent down, everything else frozen — and the results ranked by how far they moved the PEG Ratio. Read it as a map of where PEG Ratio is fragile — drawn for the example inputs, which is the map you want when deciding what to measure carefully.
- Nudge Before by ±10 % and PEG Ratio lands between 12.24% and 37.19% (sensitivity ≈58.5 %)
- Nudge After by ±10 % and PEG Ratio lands between 11.12% and 35.82% (sensitivity ≈52.6 %)
Before is the dominant lever here: ten percent either way moves the result by about 58.5 %, from 12.24% to 37.19%. Measure that input from a document rather than from memory, and treat After as the second priority (≈52.6 % per ten percent). The rest of the inputs earn only a rounding-error of attention, and that asymmetry is the practical payoff of measuring rather than asserting.
Is your PEG Ratio good — reading the result bands
Nobody acts on a bare figure — they act on a figure with a comparison attached. The default case lands in the “Solid growth” band, and bands are deliberately wide because real situations overlap. The sensitivity list shows how far a modest input error moves you along that ladder: for Before, ±10 % covers 12.24% to 37.19%. The practical reading rules: read the band as a starting hypothesis, then test it: change the two dominant inputs by ten percent and see whether the verdict survives. Verdicts that survive stress are the ones worth acting on.
In Investing & Markets, PEG Ratio is one instrument in an orchestra: on its own it is a number, next to Absolute change and Per-period (annualised) it becomes a diagnosis. The tools linked above exist so the headline never has to carry that weight alone.
How people get PEG Ratio wrong
Percentage-point vs percent confusion: a move from 4 % to 6 % is +50 % relatively but +2 points — state which you mean. 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.
Treating the example inputs as a recommendation. They are a demonstration of the mechanism — a decision-grade PEG Ratio begins the moment your own figures replace them.
Attention is also misallocated between fields. Having measured this engine, we can say where it belongs: Before first, everything else second.
Another is comparing across contexts: a PEG Ratio computed with one set of conventions should never be lined up against a figure computed with another. Check the inputs behind both before ranking them.
Six things to confirm before acting on PEG Ratio
- Confirm the example values are plausible for your own situation before replacing them.
- Recompute once with the dominant input deliberately set low, and see whether the decision changes.
- Put Before under a magnifier; the sensitivity table above is the reason why.
- Note the date and the inputs beside the number so the figure can be audited later.
- Record the date and the inputs alongside the number so future-you knows what was assumed.
- Run the ±10 % stress on the top two levers and check that your conclusion survives both.
Five steps from raw inputs to a figure you can defend
The tool does the arithmetic; the routine below is what makes the arithmetic trustworthy. Five steps, a minute total — and afterwards you will know not just what the number is, but which assumption produced it.
Step 1 — gather before you type. PEG Ratio depends on before, after, periods between (years). Collect them from a source document — a statement, a report, an invoice, a log — rather than from memory, because recalled inputs are the single largest cause of wrong results. The input you reach for first is usually the one you measured longest ago.
Step 2 — compute the version you would not be embarrassed by. If a stranger audited your inputs, which set would you hand over? Enter that set, read the result, and treat everything else as upside. Compare the calculation to the rough guess you arrived with, and ask why they differ.
Step 3 — measure what deserves measuring. The ranked levers above tell you where a careful figure pays off. Everything else can stay approximate, which is a licence to stop hunting for data you do not need. Repeating a calculation with the same numbers proves only that the arithmetic is reliable — which is worth knowing.
Step 4 — run the scenario trio. Expected, pessimistic, optimistic. The gap between pessimistic and expected is the number to plan against; the optimistic result is useful only as a ceiling. The fastest sanity test is to guess the answer first and see how far the calculation disagrees.
Step 5 — record the context, not just the number. Note today’s date and the inputs alongside the 23.47% output. Six months from now the context is what turns this figure into a trend. A figure with a date beside it becomes evidence; without one it stays an anecdote.
Where PEG Ratio matters in practice
In Stocks & Equities 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. A figure nobody can reproduce is a figure nobody will act on twice.
Professionals in Stocks & Equities use this style of calculation as a screening filter before spending real money or effort: a quick PEG Ratio check eliminates weak options in minutes, and the survivors earn the deeper, slower analysis. Say the answer out loud before you save it; if it sounds wrong, the model did not change, your understanding did.
Nothing here is stored or transmitted, so the habit of checking is free: open the page, re-enter current figures, compare with the number you saved last time. If the answer changes your behaviour, it deserves a second run with different assumptions.
The questions that come up most about PEG Ratio
What affects PEG Ratio the most?
Measured on this engine, Before is the dominant lever: moving it ±10 % shifts the PEG Ratio across 12.24% to 37.19% — about 58.5 % of the headline, with After next at ≈52.6 %. The ranked list in the sensitivity section is computed live, not asserted from a template.
Which matters more: after or before?
For PEG Ratio, Before wins the head-to-head (≈58.5 % against ≈52.6 % per ten-percent change). Knowing which input dominates is the difference between careful work and merely slow work.
What is a typical PEG Ratio?
There is no honest universal average for PEG Ratio, but there is a reference point: the defaults on this page produce 23.47% (Solid growth). Replace the inputs with your own and compare — that comparison is the useful meaning of “typical”.
How do I calculate PEG Ratio by hand?
change % = (after − before) ÷ before × 100; annualised = (after ÷ before)^(1/periods) − 1 is the entire method. Work the inputs in that order — Δ = 121.00 − 98.00 = 23.00 — and you will reach 23.47% on the default figures, the same number this tool prints.
What happens to PEG Ratio if before changes by 10 %?
The engine was re-run with that field moved by ten percent while everything else stayed fixed: the PEG Ratio goes across 12.24% to 37.19%, a swing of roughly 58.5 % around the 23.47% baseline. That ratio is the practical definition of how much this input matters.
Is the PEG Ratio result of 23.47% good or bad?
The tool answers “what”, not “whether”: 23.47% carries the verdict “Solid growth” for the default case, which is a starting interpretation rather than a verdict on your situation. Re-run with your own figures and compare the bands.
Can I predict future returns with PEG Ratio?
No tool predicts; PEG Ratio computes implications. Use it to ask "if these inputs hold, what follows" — then stress the assumptions.
Can PEG Ratio be negative or empty?
Yes, and that is informative rather than broken: a negative PEG Ratio usually means the inputs encode an outflow or a shortfall, and the verdict band above labels exactly that situation instead of hiding it.
Is percent change symmetric?
No — up 25 % needs down 20 % to undo. The multiple output keeps the round trip honest.
Why annualise?
It puts unequal time spans on one scale, making 4-year and 9-month comparisons legible.
Does this PEG Ratio tool store my numbers?
No. The entire calculation runs in your browser session; nothing entered above is transmitted or saved, which is the correct behaviour for sensitive Investing & Markets figures and the reason you can re-run this page as often as you like.
Key terms on this page
- Absolute change
- 23.00 for the PEG Ratio worked case; it sits next to the main result because it carries context the headline leaves out.
- Per-period (annualised)
- 3.58% for the PEG Ratio worked case; it sits next to the main result because it carries context the headline leaves out.
- Multiple
- 1.23 × for the PEG Ratio worked case; it sits next to the main result because it carries context the headline leaves out.
- PEG Ratio
- The primary output of this tool: 23.47% for the default inputs, computed exactly from change % = (after − before) ÷ before × 100; annualised = (after ÷ before)^(1/periods) − 1.
- Worked example
- The calculation written out in full so that nothing on this page has to be taken on trust.
- Verdict band
- The plain-language label — here “Solid growth” — mapping the computed figure onto experience-based ranges for Investing & Markets.
- Sensitivity (±10 %)
- How far the PEG Ratio moves when a single input is nudged ten percent either way; the ranked list on this page is computed live from this engine.
Method, sources and what this tool cannot tell you
Everything above runs on one stated formula, applied without hidden coefficients: change % = (after − before) ÷ before × 100; annualised = (after ÷ before)^(1/periods) − 1. Source of record: Standard growth arithmetic. 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.
This page is an estimation aid, not professional advice. The design rule is simple: two people entering identical figures must get identical answers. The sensitivity table above is part of that promise rather than a bonus: it lets you see how much of the result depends on how carefully you measured.
After the number: what to do with it
Re-run the calculation with your own figures, stress the two most sensitive inputs by ±10 %, and only then act on the result.
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.