A content gap is the set of topics your competitors have published against and you have not. Finding that set is easy arithmetic. Deciding which items in it deserve a writer's week is the part that actually matters, and it is the part most gap analyses skip entirely — they hand you a list of four hundred missing keywords sorted alphabetically and call it a strategy. This calculator does both halves: it subtracts your list from theirs, then ranks what remains by the volume you supply and the difficulty you supply, under weights you can see and change.
Arb Digital built this because gap-analysis exports arrive as raw difference lists, and the first thing anyone does with one is paste it into a spreadsheet to add a priority column. This is that spreadsheet, made repeatable. Nothing here is a Google-published metric — Google publishes no keyword volumes, difficulty index, or content priority score. The numbers are yours, and the weighting that combines them is an editable model rather than a hidden constant.
What This Content Gap Calculator Does
You paste two lists: every topic you already cover, one per line, and every topic your competitors cover, optionally with a monthly volume and difficulty appended after pipe characters. The tool normalises both — lowercasing, trimming whitespace, collapsing spaces, stripping trailing punctuation — then works out three sets: topics on both lists, topics only they have, and topics only you have.
The headline number is the size of the gap. Underneath it, the coverage percentage shows what share of their footprint you already match, the total monthly volume shows how much demand is unaddressed, and the ranked bars order every gap topic by a priority score built from your inputs. The fourth figure — topics unique to you — is the one people forget, and often the most commercially interesting, because it is the part of the market you own without contest.
How to Use It
- Export your own topic coverage first. The primary keyword for each published URL is usually the cleanest source. One topic per line, no bullets.
- Add the competitor list. Pull it from your keyword tool, or build it by hand from their sitemap and page titles for a small competitor set.
- Append volume and difficulty where you have them. Use the format keyword | volume | difficulty. Any line without numbers falls back to the two default fields, so a partial dataset still ranks sensibly.
- Set the two weights. Raise the volume weight if you have the authority to compete on hard terms. Raise the ease weight if you need results from a young site and cannot afford long fights.
- Read the ranked bars, not just the count. The order is the output. The gap count is only the headline.
The Formula / How It's Calculated
Set matching comes first. Each line is normalised to lowercase, stripped of leading and trailing whitespace and punctuation, and internal runs of spaces are collapsed to one. Two lines match if their normalised forms are identical. The gap is the competitor set minus the intersection.
Coverage % = (topics on both lists ÷ total competitor topics) × 100
Each gap topic then gets a priority score on a 0–100 scale. Volume is scored relative to the largest volume in the gap, so the biggest term in your own dataset anchors the top of the scale rather than an arbitrary industry number. Difficulty is inverted into an ease score, because low difficulty should push a topic up the list, not down.
Priority = (VolumeScore × VolumeWeight + EaseScore × EaseWeight) ÷ (VolumeWeight + EaseWeight)
Where VolumeScore = 100 × volume ÷ highest gap volume and EaseScore = 100 − difficulty. Take the defaults as a worked example. The largest gap volume is 3,600 for "schema markup guide", so it scores 100 on volume; its difficulty of 38 gives an ease score of 62. Under 60/40 weights: (100 × 60 + 62 × 40) ÷ 100 = 84.8. "Site migration checklist" at 880 volume scores 24.4 on volume and 71 on ease, giving 43.1. Shift the weights to 30/70 and the gap between them narrows sharply — which is the point of making the weights visible.
Dividing by the sum of the weights means they need not add up to 100. Weights of 6 and 4 behave identically to 60 and 40; only the ratio matters.
Why the Raw Gap Count Is the Least Useful Number
A gap of 400 topics and a gap of 12 can represent the same commercial opportunity, because gap size is a function of how many competitors you exported and how deep you went into their long tail. Add one competitor and the count jumps; filter to pages with real traffic and it collapses. The number moves for reasons unrelated to your business.
What does not move arbitrarily is the ordering. If "schema markup guide" sits above "international seo hreflang" under your weights, it will keep sitting above it whether you exported three competitors or thirty, because the ranking is driven by the volume and difficulty attached to each topic rather than by the population size. Treat the count as context for a slide and the ordering as the actual deliverable.
The coverage percentage is the one aggregate worth tracking over time, and only against a frozen competitor set. Re-run it against a different set and it measures nothing at all.
The Boundary With Clustering and Topical Authority
Three tools on this site touch the same territory and answer genuinely different questions, so it is worth being precise about which one to reach for.
This calculator answers what is missing. It compares two flat lists and ranks the difference. It has no opinion about how the missing topics relate to each other.
The keyword cluster generator answers what belongs together. Feed it the gap list this tool produces and it groups the terms into clusters that should live on one page rather than five, which is what stops a gap analysis turning into forty thin articles competing with each other. Run it after this tool, not instead of it.
The topical authority calculator answers how completely you cover a subject in absolute terms, against the full shape of a topic rather than against a named rival. A site can have a tiny gap against one weak competitor and still have poor topical coverage overall, because the competitor never covered the subject properly either. Use that tool when the question is depth; use this one when the question is a specific opponent.
One more boundary: if the gap turns up topics you already cover under different phrasing, you have a matching problem, not a gap. The keyword cannibalization checker handles that, because publishing a "new" page for a covered topic is how two of your own URLs end up splitting one query.
Gaps That Are Not Worth Closing
Not every missing topic is an opportunity, and a ranked list will happily put a bad idea at the top if the volume is large enough. Four categories deserve manual removal before you brief anything.
Topics outside your business model. A competitor selling both software and consultancy will rank for consultancy queries you have no product for. High volume, zero value. The calculator cannot know this; you can.
Topics where the SERP is not editorial. If the results page for a term is entirely product listings, a local pack, or a Google feature that occupies the visible area, an article will not capture the demand even ranked first. Check what the results page actually looks like before committing, and check your existing performance data in the reports documented in Search Console Help to see whether similar terms already send you clicks.
Topics the competitor is also failing at. A rival having a page is not evidence the page works. Gap analysis measures publication, not performance, and copying a competitor's unsuccessful content strategy is a common and expensive error.
Topics you covered and retired deliberately. If a page was consolidated or pruned for a reason, it will reappear in every gap analysis forever unless you keep a documented exclusion list.
Turning the Ranked List Into a Publishing Order
The priority score gives you a sequence, but a plan needs one more layer: how long each item takes. A 3,000-word piece with commissioned research and a 600-word definitional page can score near-identically while representing a tenfold difference in cost. Sorting by priority alone front-loads your calendar with the expensive items.
A practical approach is to take the top fifteen or twenty from the ranking, estimate effort in days for each, and then order by score divided by effort. That ratio surfaces the fast wins the raw score buries.
It also helps to interleave. Publishing five pages in one cluster before moving to the next builds a coherent internal linking structure as you go, and the internal link opportunity calculator will show you where the new pages should connect back into the existing site rather than sitting as orphans. Publishing one page from each of five clusters produces the same word count and a much weaker structure.
Finally, decide up front what happens to the gap list you do not action. Keeping rejected items with a one-line reason turns the next run into a five-minute job rather than a repeat of the first.
What This Calculator Cannot Tell You
It cannot tell you whether your version of a topic will beat the one already ranking, and quality decides the outcome. It cannot price a visitor, so a 4,000-volume informational term outranks a 200-volume purchase-intent term here even when the second is worth more. If revenue is the question, model it separately with the SEO ROI calculator and forecast the traffic side with the SEO traffic forecast calculator.
It also inherits every flaw in the data you paste. Volume figures from any provider are estimates derived from sampled data, and difficulty scores are proprietary composites that differ between vendors — a difficulty of 40 in one tool is not a difficulty of 40 in another. Google's own guidance on creating helpful content is explicit that content should be produced for people rather than assembled to fill a keyword list, and a gap analysis is at its most dangerous when it is treated as a commissioning queue rather than as evidence to argue with.
Arb Digital's SEO team runs gap analysis against a named competitor set, clusters the result, prices the work by effort, and publishes in an order that builds internal structure as it goes.
SEO Services Talk to Arb DigitalCommon Mistakes to Avoid
- Comparing against the wrong competitors — the sites ranking for your terms are the relevant set, not the companies your sales team names as rivals. The two lists overlap less often than people expect.
- Treating the gap as a commissioning queue without removing topics that are off-model, non-editorial, or already covered under different phrasing.
- Mixing difficulty scores from two different vendors in one list, which makes the ease half of the ranking meaningless because the scales are not comparable.
- Ignoring the "unique to you" figure — the topics only you cover are your defensible ground, and they usually deserve reinforcement before you chase someone else's list.
- Re-running against a different competitor set and reporting the coverage change as progress. Freeze the comparison set or the trend line means nothing.
Related Free Tools From Arb Digital
Cluster the gap with the keyword cluster generator, then sort the resulting terms by search intent using the keyword intent classifier so informational and transactional topics do not end up on the same page. If existing pages are slipping while you plan new ones, the content decay calculator shows whether a refresh outranks a new brief. The full free online tools hub has the rest.
Frequently Asked Questions
It is a comparison between the topics you publish against and the topics your competitors publish against, producing the set they cover and you do not. On its own it is a difference calculation; it becomes useful when the difference is ranked by demand and difficulty so you can decide what to write first.
You supply them. Google does not publish a keyword difficulty index, and volume figures from any provider are modelled estimates rather than exact counts. This tool deliberately takes both as inputs so the source stays yours and visible, rather than being hidden inside a score.
No. The 60/40 volume-to-ease split is Arb Digital's modelled default and nothing more. Google publishes no priority formula for content planning. The fields are editable precisely so you can set a ratio that matches your site's authority and your tolerance for competitive terms.
Three to five sites that actually rank for your target terms usually gives a stable picture. One competitor produces a gap shaped by that company's quirks; twenty produces a list too long to action and dominated by long-tail noise from businesses unlike yours.
Matching is exact after normalisation, so "seo audit checklist" matches "SEO Audit Checklist " but not "seo audit check list" or "checklist for seo audits". Near-duplicates are deliberately left unmatched rather than guessed at, because a false match hides a genuine gap. Tidy the phrasing in both lists for the cleanest result.
No. A gap list includes topics outside your business model, topics where the results page leaves no room for an article, and topics your competitor is also failing at. Filter manually before briefing anything — the calculator ranks what you give it and cannot judge commercial fit.
Quarterly suits most programmes, because that is roughly how long it takes for a batch of new pages to be published and indexed. Re-run against the same frozen competitor list each time, or the coverage percentage will move for reasons unrelated to anything you did.
Priority scores produced by this tool are a planning model from Arb Digital, not a metric published or endorsed by any search engine, and they do not predict rankings or traffic.
