Most tax calculators work one way: you enter a price, they add the tax. This HST Calculator solves in all three directions. Your visitor types into whichever field they actually have a number for — the price including HST, the price excluding HST, or the HST amount alone — and the other two fill themselves in instantly.

That matters more than it sounds. Working backwards from a receipt total, or from a tax figure on an invoice, is the case most calculators simply cannot handle.

Three more things set it apart:

You control the tax rates. Provincial rates change — Nova Scotia went from 15% to 14% in April 2025. Edit any rate from the settings screen, rename a province, or add one. You are never waiting on a plugin update to stay accurate.
Five ways to place it, from one install: shortcode, block, sidebar widget, automatic insertion into posts, and a floating button.
Saving settings clears your page cache automatically, across sixteen caching plugins — so a colour or rate change is live immediately instead of leaving you wondering why nothing changed.

How it works

Your visitor picks a province and types an amount into any one of three fields:

Price including HST
Price excluding HST
HST amount

The other two are worked out instantly, in the browser. No page reload and no server request, so it behaves identically on cached pages.

Made to match your theme

Every colour is a setting: background, borders, text, title, field labels, field background, the accent colour used for buttons and focus rings, and the highlighted HST row. Corner rounding, border thickness, width, text size and alignment are settings too. You can also set colours per block, so one page can look different from another.

Five ways to place it

Shortcode — [fizzhstc_calculator] in any page, post or text widget
Block — search “HST Calculator” or “FizzyTech” in the block editor
Widget — Appearance Widgets, for sidebars and footers
Automatic — add it to every post of the types you choose
Floating button — a small button in the corner of every page

Using Elementor, Divi, WPBakery or Beaver Builder? Each has a Shortcode element — drop one in and paste [fizzhstc_calculator].

Rates you control

Ontario, New Brunswick, Newfoundland and Labrador, Nova Scotia and Prince Edward Island are built in. Rates do change — Nova Scotia went from 15% to 14% in April 2025 — so you can edit any rate, rename a province, or add one, right from the settings screen. No plugin update needed.

Cache-aware

Settings-driven markup and page caching are an awkward pair: a cached page keeps serving the old colours until something clears it. Saving settings here clears the cache for you — WP Rocket, W3 Total Cache, WP Super Cache, LiteSpeed, WP Fastest Cache, SiteGround Optimizer, Cache Enabler, WP-Optimize, Breeze, Hummingbird, Comet Cache, Swift Performance, Autoptimize, Nginx Helper, Kinsta and Pagely. There is a manual “Clear page cache” button too.

Everything is included

No paid tier, no locked features, no trial. Every feature described here works from the moment you activate it.

Privacy

The plugin makes no external requests, sets no cookies and collects no data. Calculations happen in the visitor’s browser.

FizzyTech HST Calculator