Free embeddable widgets
Add a calculator to your blog
in one line of HTML.
Drop one of our calculators into your post, newsletter, or course module. No signup. No API key. No fees. Your readers get an instant interactive tool: you get a quietly attributed link back to Blacknave.
Free forever · No attribution required (but appreciated) · Updates automatically
Zero setup
Paste one iframe. Works in WordPress, Substack, Notion, Ghost, plain HTML, anywhere iframes are allowed.
Reader-first UX
Same dark theme, same fast app, same offline-friendly localStorage that powers blacknave.com.
Always current
When we ship a fix or improvement, every embed updates automatically. You never re-paste anything.
Available widgets
Pick a calculator. Copy the snippet.
Live previews below mirror exactly what your readers will see. The footer's subtle Blacknave attribution is the only Blacknave chrome on the embedded page: everything else is your reader and the tool.
TDEE & Macro Calculator
Daily calorie target and protein / carbs / fat split based on weight, activity, and goal. Recalculates instantly as the reader adjusts inputs. Perfect for fitness blogs, nutrition pages, cutting and bulking guides.
<iframe src="https://blacknave.com/previews/tdee-macro.html?embed=1" width="100%" height="720" frameborder="0" style="border:1px solid #242424;border-radius:12px;background:#0a0a0a;max-width:780px;width:100%" loading="lazy" title="TDEE & Macro Calculator by Blacknave"></iframe>
Drop this iframe in any HTML page. Width is fluid (100% up to 780px max); adjust height if your layout is taller or shorter.
Debt Payoff Planner
Reader enters their debts, picks avalanche or snowball, and sees their exact debt-free date plus total interest paid. Side-by-side method comparison. Ideal for personal-finance blogs, debt-free communities, FIRE content.
<iframe src="https://blacknave.com/previews/debt-payoff.html?embed=1" width="100%" height="780" frameborder="0" style="border:1px solid #242424;border-radius:12px;background:#0a0a0a;max-width:780px;width:100%" loading="lazy" title="Debt Payoff Planner by Blacknave"></iframe>
Drop this iframe in any HTML page. Width is fluid (100% up to 780px max); adjust height if your layout is taller or shorter.
How it works
- 1
Pick a widget
Browse the gallery above and find the calculator that fits your post.
- 2
Copy the iframe
One click on the Copy button. The snippet is plain HTML: no script tags, no CSS to wire up, no API key.
- 3
Paste in your editor
Drop into your CMS’s HTML / embed block. WordPress (Custom HTML), Substack (HTML embed), Ghost (HTML card), Notion, Webflow, plain HTML: all supported.
- 4
Done
Your readers get an interactive tool. The tiny footer credits Blacknave and links back: that’s the entire arrangement.
Common questions
Is this really free?+
Yes. No signup, no API key, no rate limits, no fees. We make money on the small percentage of readers who click through and become paying members of Blacknave: that’s why the footer exists.
Can I remove the "Powered by Blacknave" footer?+
The footer is the entire deal: keep it, and the widget is yours to use forever. If you want a clean white-label embed without the footer, contact help@blacknave.com to discuss a paid licence.
Will the widgets break my page?+
No. Each widget is loaded in an isolated iframe, so its CSS and JavaScript can’t affect the rest of your page. Width is fluid (100% up to 780px max), so it adapts to your content column.
Do you track my readers?+
Only the same first-party analytics we use on blacknave.com (anonymous Vercel pageviews + optional PostHog if it’s configured). No cross-site tracking, no third-party ad pixels.
What if I want a custom widget for my niche?+
If you publish in a fitness, finance, or career niche and have an audience, email help@blacknave.com. We build occasional bespoke widgets in exchange for a long-term embed agreement.
Does the widget work on mobile?+
Yes. Each calculator is built mobile-first and tested on iOS Safari + Android Chrome. Inputs are 16px so iOS doesn’t auto-zoom.
Can I combine this with the affiliate program?+
Yes, and we recommend it. Embed the widget, then drop your affiliate link in the surrounding post (e.g. "want the AI version? Try Blacknave free"). You earn 25% recurring on every reader who upgrades.
How do I report a bug or request a new calculator?+
Email help@blacknave.com. We ship fixes within a few days; new calculators land based on demand.
Browse all 21 interactive apps
The two widgets above are the embeddable cut. The full Blacknave subscription adds AI coaching, cross-device sync, and 19 more tools across fitness, finance, career, and lifestyle.
Questions? Email help@blacknave.com