Google Keyword Planner vs SEMrush vs Ahrefs for PPC Keyword Research: Which Tool Should You Use?

Jesse Heslinga
Jul 28
10 min read

Most Google Ads keyword research starts in the same place: Google Keyword Planner. It is free, it comes built into Google Ads, and it is the only tool that pulls data straight from Google's own auction. Then someone tells you to upgrade to SEMrush or Ahrefs, and you wonder whether it is worth it.

I use all three in different parts of the workflow. They are not interchangeable, and picking the wrong one for the wrong job costs you time or money.

I run paid search, not SEO, so read this with that context.

The Short Answer

Google Keyword Planner is the starting point for PPC keyword research. Free, uses Google's actual auction data, and the only tool that gives you Google-source CPC estimates. The limitation is volume ranges instead of precise numbers, and no competitive intelligence at all.
SEMrush is the best complement for PPC work. It surfaces keywords Keyword Planner misses, shows what competitors bid on, and gives specific volume numbers. Worth adding when you need the competitive layer.
Ahrefs is the weakest of the three for PPC keyword research specifically. Strong for organic SEO, but no bid simulation, no budget forecasting, and limited PPC-specific data. Buy it for SEO, not for Google Ads.
For most lead-gen businesses: start with Keyword Planner (you already have it), and add SEMrush if you want competitive keyword gaps. Ahrefs only if you also run SEO campaigns.

The honest answer: it depends on what job you are doing

Google Keyword Planner is a PPC planning tool. Its job is to help you find keywords to bid on, estimate CPCs, and forecast traffic for a Google Ads campaign. It is very good at that.

SEMrush and Ahrefs are broader research platforms. They do keyword research across paid and organic, competitive analysis, content research, site audits, and more. Neither was built specifically for PPC, though SEMrush comes much closer than Ahrefs.

The decision is simpler than it looks. Use Keyword Planner as the foundation of any PPC keyword build: it gives you Google's real CPC data, which the others can only estimate. Add SEMrush when you want to find what competitors bid on, discover keyword clusters the native tool misses, and get precise volume numbers rather than broad ranges. Leave Ahrefs for SEO work.

Pro Tip: When you have an active Google Ads account with consistent spend, Keyword Planner shows precise volume numbers instead of ranges. Without active spend, you get buckets like "1K-10K" which makes prioritisation hard. If you are just starting, that is the first reason to complement it with a paid tool.

How each tool actually works

Google Keyword Planner is built into Google Ads and free for anyone with a Google account. It works by showing you keyword suggestions based on a seed term or URL, along with average monthly search volumes, competition level (Low/Medium/High based on advertiser density, not organic difficulty), and suggested bid ranges pulled directly from Google's auction data. When your account has consistent spend, volumes become precise monthly averages. With low or no spend, they become broad ranges.

The CPC data is the thing no third-party tool can replicate: it comes from Google's actual auction, not an estimate. That makes Keyword Planner the most reliable source for bid planning and budget forecasting in Google Ads.

SEMrush builds its keyword database from a combination of clickstream data, web crawls, and third-party data sources. It shows specific monthly volume numbers (rather than ranges), CPC estimates, keyword difficulty, and competitive data including which domains bid on each term and what they pay. Its Keyword Gap tool compares your domain against competitors and surfaces keywords they rank for that you do not target, in both paid and organic.

For PPC work specifically, SEMrush is useful beyond Keyword Planner for two jobs: finding keyword clusters competitors are bidding on that you have not built campaigns around yet, and getting more granular volume data to prioritise between terms.

Ahrefs is built for organic SEO research. Its keyword database is large and its difficulty metrics are considered among the most accurate in the industry. For PPC work, it shows whether a keyword has paid ads appearing, the estimated CPC, and the keywords a competitor's domain bids on via a "Paid keywords" tab. But it does not support bid simulation, budget planning, match-type modeling, or campaign structure workflows. The PPC data is thin compared to what SEMrush or Keyword Planner offer.

What the numbers say

The tools sit at very different price points.

Tool	Cost	Data source
Google Keyword Planner	Free	Google's own auction data
SEMrush	$139.95/month (Pro) to $499.95/month (Business)	Clickstream + third-party estimates
Ahrefs	$129/month (Lite) to $449/month (Advanced)	Clickstream + web crawls

Annual billing reduces SEMrush and Ahrefs costs by roughly 16-17%. Semrush One bundle starts at $199/month combining SEO and AI visibility tools.

Figures are directional; verify current pricing before committing.

On accuracy, the picture is not straightforward. Ahrefs published research showing that 91% of Google Keyword Planner volumes are overestimations, often significantly. A 2026 industry comparison found SEMrush volume estimates to be closer to actual click data in many cases. But Google Keyword Planner's CPC data, sourced directly from the auction, is more accurate for bid planning than either of their estimates.

The short version: Keyword Planner is unreliable on volume but reliable on CPCs. SEMrush and Ahrefs are reasonable on volume but estimating on CPCs. Know which number you need and pick the tool accordingly.

Where the tools actually split: what Keyword Planner hides

Google Keyword Planner has a tendency to group keywords together. "Roof repair London" and "roof replacement London" might be shown as the same keyword with a combined volume, hiding which term actually drives more searches. Close variants collapse into each other, making it hard to prioritise between them.

It also only surfaces what Google's algorithm thinks is relevant to your seed terms or URL. If there is a keyword cluster that competitors target but you have not discovered yet, Keyword Planner will probably not surface it because it has no competitive data at all.

SEMrush's Keyword Gap tool does what Keyword Planner cannot: it compares your domain (or a competitor's) against other domains and shows every keyword they bid on that you do not. For a lead-gen business entering a competitive local market, that gap analysis often surfaces 20-40% more relevant keywords than Keyword Planner's suggestions alone.

Keep in Mind: SEMrush and Ahrefs volume numbers look more precise than Keyword Planner's ranges, but they are still estimates built from third-party data. A keyword showing 1,200 searches/month in SEMrush might actually get 600 or 2,000. Treat them as directional. The CPC estimates from Keyword Planner are more reliable for budget planning.

Google Keyword Planner vs SEMrush vs Ahrefs, side by side

Dimension	Google Keyword Planner	SEMrush	Ahrefs
Price	Free	$139.95/month+	$129/month+
Data source	Google's own auction	Clickstream estimates	Clickstream + crawls
Volume accuracy	Ranges (imprecise)	Specific numbers (estimates)	Specific numbers (estimated, strong on organic)
CPC accuracy	High (Google's auction)	Estimated	Estimated
Competitive intelligence	None	Strong	Limited for PPC
Keyword gap analysis	None	Yes	Limited for paid
PPC-specific features	Bid simulation, budget forecasting	Advertising Research module	Basic paid tab only
Best at	PPC planning, bid estimates	PPC + SEO combined research	Organic SEO

Reading this table: Keyword Planner wins on price and CPC accuracy. SEMrush wins on breadth and competitive intelligence. Ahrefs wins on organic SEO but lags for PPC-specific work. None replaces the others entirely for a full keyword research workflow.

When Google Keyword Planner wins

Use Keyword Planner as the foundation for any PPC keyword build, regardless of what else you use:

It is the only tool with actual Google auction data for CPCs. For budget planning, there is no substitute.
For bid simulation and traffic forecasting before launching a campaign, Keyword Planner's native forecasting tool pulls from real Google data.
If you are just starting with Google Ads and have not budgeted for a paid keyword tool, Keyword Planner is genuinely capable. Most small lead-gen accounts can run a solid keyword strategy with it alone.
For accounts with consistent spend, the volume data becomes precise rather than range-based, closing the biggest gap.

Verdict: Keyword Planner is the non-negotiable starting tool for Google Ads keyword research. Not because it is better than the paid tools overall, but because it has Google's own data and costs nothing.

When SEMrush wins

Add SEMrush when:

You want to see what competitors bid on and find keyword clusters you are missing
You need specific volume numbers (not ranges) to prioritise between terms in a new market
You manage both paid and organic campaigns and want a single platform
You are taking over a new account and need to quickly map out what competitors target in paid search

For a lead-gen business in a competitive local market, the SEMrush Keyword Gap analysis is the strongest complement to Keyword Planner. It finds the terms you are not targeting that competitors already pay for, which shortens the time to finding what works.

Verdict: SEMrush earns its cost when you need competitive keyword intelligence or precise volume data on top of Keyword Planner's CPC foundation.

Common mistake: Using only Google Keyword Planner and assuming you have found all the relevant keywords. You have found the keywords Google thinks are relevant to your seed terms. That is not the same as the full competitive keyword set.

When Ahrefs wins

For PPC keyword research specifically, Ahrefs does not win compared to Keyword Planner or SEMrush.

If you already subscribe to Ahrefs for organic work, the paid keywords tab gives a quick check on what a competitor bids on. Useful context. Not a reason to use Ahrefs as your primary PPC research tool.

Ahrefs has no bid simulation, no budget forecasting, and no match-type modeling. For the keyword planning jobs that matter most in Google Ads, Keyword Planner does more, for free.

Where Ahrefs genuinely helps in a PPC workflow is on the organic side of a combined paid-organic strategy: finding keywords with high organic potential that you can convert to paid quickly while SEO builds. For businesses deciding whether to run Google Ads or invest in SEO first, Ahrefs data is relevant. For pure PPC keyword builds, it is not the tool.

Verdict: Buy Ahrefs for SEO. Use Keyword Planner and SEMrush for PPC keyword research.

Common mistakes

Trusting Keyword Planner volume ranges as if they were precise. A "1K-10K" range could mean 1,200 searches or 9,500. Complementing with SEMrush volume data gives a better read before committing budget.
Ignoring the competitive density column in Keyword Planner. "High" competition means a lot of advertisers are bidding on that term, which pushes CPCs up. This is useful signal before you set a budget.
Using SEMrush volume data for PPC bid planning instead of Keyword Planner's CPC estimates. SEMrush is better at volumes; Keyword Planner is better at bid ranges. Use each for what it does well.
Picking one tool and never using the other. The strongest keyword research process for a Google Ads lead-gen account uses Keyword Planner for bid and volume validation and SEMrush (or SpyFu) for competitive gaps.
Skipping keyword research entirely on account takeovers. Moving into a new account without a fresh keyword gap analysis against competitors means you inherit whatever the previous manager decided, gaps and all.

How I handle this for lead-gen businesses

For any new account or market, the keyword research process starts in Google Keyword Planner: seed terms based on the client's services and service area, volume check, and a read on CPCs and competition level to size the opportunity. Then competitive gap analysis, usually in SEMrush or SpyFu, to find what the top local competitors target that we do not.

The two tools do different jobs. Keyword Planner gives the CPC reality check and the Google-sourced foundation. SEMrush fills the gaps the native tool misses.

Ahrefs stays in the organic work. If I am advising a client on whether setting a Google Ads budget makes sense given their competitive situation, that keyword research step is part of the answer: how competitive is the market, what are CPCs likely to be, and what is the realistic cost per lead based on those inputs.

Ready to build a keyword strategy that fits your market? If you want a keyword audit for your account, including a competitive gap analysis, that is part of every account review I do.

Book a free account review

Frequently Asked Questions

Is Google Keyword Planner accurate enough for PPC keyword research?

For CPC estimates and bid planning, Keyword Planner is the most accurate tool available because it uses Google's own auction data. For volume estimates, it is less reliable: it shows ranges rather than precise numbers when account spend is low, and a study by Ahrefs found that 91% of Keyword Planner volumes are overestimations. Use it for CPCs; complement with SEMrush for more granular volume data.

Do I need SEMrush if I already use Google Keyword Planner?

Not necessarily. For smaller lead-gen accounts in less competitive markets, Keyword Planner is enough for initial keyword research. SEMrush adds value when you want to see what competitors bid on (keyword gap analysis), get precise volume numbers rather than ranges, and find keyword clusters Keyword Planner does not surface from seed terms. If budget is the constraint, start with Keyword Planner alone and add SEMrush when you outgrow it.

Can Ahrefs replace Google Keyword Planner for PPC?

No. Ahrefs does not have bid simulation, budget forecasting, or Google-source CPC data. Its paid keyword tab shows what competitors bid on and rough CPC estimates, but the data is thinner than SEMrush's and it lacks the PPC planning features in Keyword Planner. Use Ahrefs for organic SEO research and keep Keyword Planner (free) for PPC planning.

How do SEMrush and Ahrefs calculate keyword search volume?

Both use clickstream data combined with web crawl data to estimate monthly search volumes. Neither has direct access to Google's search data. This means their volume numbers are specific but estimated, while Keyword Planner's ranges come from actual Google queries. Treat all three as directional inputs, not precise figures.

Which tool is better for finding long-tail PPC keywords?

SEMrush surfaces more long-tail variations than Keyword Planner because it builds its database from competitor domains, not just seed-term suggestions. Running a competitor domain through SEMrush's Organic Research or Paid Research tabs shows every keyword that domain targets, including long-tail terms Keyword Planner would not suggest. For a lead-gen business building out service-plus-location keyword combinations, that approach consistently surfaces gaps.

Does Ahrefs show Google Ads keyword data?

Ahrefs shows which keywords have paid ads appearing in search results and estimates the CPC, but its primary database is built for organic SEO. The paid data is a secondary feature. For Google Ads-specific keyword research, Google Keyword Planner and SEMrush are more relevant.

About the author

Jesse Heslinga | Google Partner | 7+ Years Google Ads | Lead-Gen Expert

I run Google Ads for lead-gen service businesses at Groove Media across clinics, home services, and professional services, working with clients directly, no account-manager layer. I build every account around one question: is this spend turning into real customers, not just cheap form fills?