Best one page calculator websites
Single-intent calculator sites are one of the simplest SEO projects you can build. They usually consist of one core calculator, a short explanation, a few FAQs, and annual updates. Because the user intent is “I just want the number”, you can compete with much larger brands if the calculator is accurate and loads quickly. They are also relatively safe from zero-click searches as AI Overviews and search results cannot replicate their functionality (for now!)
Here are some examples of my favourite one-page calculator sites to give you some inspiration to get your own site set up.
EV Tax Calculator
https://evtaxcalculator.co.uk/
An electric vehicle tax calculator focused on the "per mile" tax due to be introduced in UK in 2028.
- Strengths: Exact-match domain, ultra clear intent, minimal distractions, fast loading.
- There is currently search volume for this which is only going to increase over the next 2 years when the new tax is introduced. Building this early has helped to get ahead of the competition.
UK Salary Calculator
A take-home pay calculator that estimates net salary after tax, National Insurance and pension deductions. Users can quickly compare gross vs net income.
- Strengths: Massive search volume, evergreen demand, and strong informational intent.
- Why it works as a side gig: Annual tax updates create easy “freshness” wins in SEO, and the tool naturally expands into related calculators (bonus tax, overtime, pensions).
Stamp Duty Calculator
https://stampdutycalculator.co.uk/
A property purchase calculator estimating stamp duty costs based on purchase price, buyer type and region. Often used during high-stress decision moments.
- Strengths: High CPC keywords, clear transactional intent, and strong seasonal surges.
- Why it works as a side gig: Property keywords attract valuable ad revenue and affiliate opportunities, while the calculator itself remains technically simple.
Day Rate Calculator
https://dayratecalculator.com/
A freelance-focused tool that converts annual salary goals into a daily or hourly rate, helping contractors and consultants price their services.
- Strengths: Niche audience with strong intent and high engagement time.
- Why it works as a side gig: Perfect overlap with tech, SEO and freelance communities, creating natural shareability and backlink potential.
Word Counter
A simple text utility that counts words, characters and reading time in real-time as users type or paste content.
- Strengths: Extremely broad demand, instant gratification and repeat usage.
- Why it works as a side gig: Demonstrates how even very simple utilities can generate large traffic volumes with minimal ongoing maintenance.
Concrete Calculator
https://concretecalculator.uk/
A construction-focused calculator estimating how much concrete is required for slabs, footings or posts based on dimensions.
- Strengths: Industry-specific intent, low competition compared to finance niches, and strong practical value.
- Why it works as a side gig: B2B and DIY audiences convert well for affiliate links, and the maths is straightforward while the perceived usefulness is high.
Why Calculator sites make good SEO side-gigs
- Exact match domains still work for SEO, especially for functional tools with clear intent
- Freedom to go into more depth than competitors with FAQs, examples and edge-cases
- Binary user intent – visitors want a number or answer now, which drives high click-through rates
- Low content requirements compared to blogs or ecommerce sites
- Evergreen traffic with predictable seasonal spikes
- Simple tech stack – most calculators can be built with basic JavaScript and HTML. With AI, you only need the most basic technical knowledge.
- Easy monetisation via display ads, affiliate links or lead capture
Tips for building your own
- Find your niche: Look for high-intent keywords where users need a number, not an article.
- Keep it simple: One page, one purpose. Avoid feature bloat.
- Understand user pain points: What are the extra levels of detail which your competitors are missing?
- Use an exact-match or partial-match domain: It still helps with click-through and trust.
- Add FAQs and examples: Capture long-tail traffic without turning it into a blog.
- Cite your sources: State where the data behind the calculator is coming from. Make sure to keep it up to date.
- Update annually: Freshness signals are easy wins for calculator sites.
- Monetise lightly: Display ads or a single affiliate partner often outperform clutter.