Most articles that show up for "Shopify AI size recommendation app" stop at a price table. But the first thing that actually trips up a merchant isn't the price — it's whether AI is even turned on at that price.

We checked three apps on the Shopify App Store (en-US locale) on September 6, 2026, and found that this line is drawn in a completely different place for each one. AI Fit Finder Size Recommender by CartCoders includes AI recommendations starting on its cheapest $9.99 plan. Kiwi Size Chart & Recommender and SmartSize, on the other hand, have no AI feature at all on their free or entry-level tiers — you have to move up to $14.99 and $19 plans, respectively, before the AI engine turns on.

What Shopify handles natively

Shopify has no feature named "size recommendation." The official Shopify Help Center tutorial, "Adding a pop-up size chart to your product pages," shows how to create a page-reference product metafield and connect it to a Pop-up block in the theme, which pulls in a page from Online Store. What this produces is a static size chart you pre-build and display on the product page — nothing more.

A feature where a shopper enters their height, weight, age, and fit preference and an AI engine replies "you're a Medium" is not part of that workflow. Shopify's metafield system has no table data type, and its documentation for rich text metafields explicitly limits formatting to headings, lists, links, bold, and italics. The moment personalized size recommendation is the goal, it's outside what native Shopify handles.

If you need the mechanics of building a static size chart itself — including the documented limit that only one page can be linked per product metafield — that's a separate topic we've covered elsewhere. This article focuses specifically on the layer above that: AI-driven, per-shopper size recommendations.

Scope of this comparison

We looked at three apps whose Shopify App Store (en-US) listings explicitly describe an AI-powered size recommendation feature:

• AI Fit Finder Size Recommender (developer: CartCoders, based in Scottsdale, Arizona)
• Kiwi Size Chart & Recommender (developer: Staytuned, based in New York)
• Smart Size Chart & Fit Finder (developer: SmartSize, holds the Built for Shopify badge)

All pricing and feature details below come from the official Shopify App Store listings (en-US), checked September 6, 2026.

Comparison table

	AI Fit Finder Size Recommender	Kiwi Size Chart & Recommender	Smart Size Chart & Fit Finder
Developer	CartCoders (US)	Staytuned (US)	SmartSize
Built for Shopify	Not shown	No	Yes
Rating (reviews)	5.0 (21)	4.7 (1,188)	5.0 (133)
Free plan	None	Yes (3 charts, Kiwi watermark)	Yes (2 charts)
Cheapest plan with AI recommendations	S: $9.99/month (all plans)	Plus: $14.99/month and up	Pro 100: $19/month
Free trial	14 days	14 days (paid plans only)	14 days (paid plans only)
Usage-based overage	Yes (charged per order above plan allowance)	Yes (Plus and up; cap not disclosed)	Pro 100 capped at 100 users/month, then upsell to a higher tier

AI Fit Finder Size Recommender (CartCoders)

The defining trait here is that AI Size Recommendations ship on every plan, starting at the $9.99/month S tier. The tiers don't differ by whether AI is included — they differ by product count (50 / 200 / 500 / 1,000 active products for S / M / L / XL) and included monthly orders (100 / 250 / 500 / 1,000, with overage billed at $0.01–$0.02 per order beyond that).

Inputs include height, weight, age, and fit preference, plus foot length and width for footwear. The listing also documents compatibility with page builders including PageFly, GemPages, and Shogun. There's no free plan — only a 14-day free trial on every tier. Launched December 27, 2024, it's the newest of the three, and its 21 reviews are all five stars. Its data-access disclosure covers customer data, products, the last 60 days of order history, and Online Store editing.

Kiwi Size Chart & Recommender (Staytuned)

Launched in March 2018 and carrying 1,188 reviews — the largest track record of the three — Kiwi's AI feature is absent from both its Free plan and its $7.99/month Premium plan. The "machine learning-powered size recommender" only becomes available at Plus ($14.99/month, up to 10 custom recommenders), and goes unlimited at Ultimate ($26.99/month).

One pricing detail is worth flagging. The Plus and Ultimate listings both note additional charges tied to order volume, but the cap on that charge is not published on the listing. A review dated August 4, 2026, from a merchant using the app for over four years, describes accidentally upgrading a plan and seeing their bill jump from roughly $5–7/month to about $150/month. Staytuned replied acknowledging the issue and offered to work with the merchant directly. That's a single review, not a pattern we can generalize — but it's a concrete reason to confirm your expected bill with the developer before moving to an order-based tier as your store grows.

Smart Size Chart & Fit Finder (SmartSize)

The only one of the three holding the Built for Shopify badge, with a 5.0 rating across 133 reviews (96% five-star). Free (2 charts), Starter ($9/month, 10 charts), and Growth ($12/month, unlimited charts) all lack size-recommendation AI — what they offer instead is static charts, multi-language display, AI-assisted translation, and a fit-scale (true-to-size) indicator.

The AI-driven "Find my size" quiz only unlocks at Pro 100 ($19/month). The listing describes it as "100 users/month – Unlimited fit quiz," which suggests the cap is 100 users per month, not 100 quiz completions — worth reading carefully, since those aren't the same unit. Answers are remembered per customer and carried over to future visits. Stores expecting to exceed 100 users a month appear to need a higher tier sold directly through smartsize.io (Pro 250 through 10K), but that pricing isn't published on the Shopify App Store listing itself — check the developer's own pricing page before committing.

How to decide

If you want AI recommendations available from day one and your catalog and order volume are still small, AI Fit Finder Size Recommender is the simplest entry point — AI is included even on the cheapest tier, so you're not choosing a plan based on whether the feature exists. Just account for the lack of a free plan and model out the per-order overage before your order volume grows.

If a large, established review base and long operating history matter more to you, Kiwi remains a reasonable option — but its AI feature only exists at Plus ($14.99/month) or above, and you should confirm the order-volume charge directly with Kiwi before your store scales. The listing's "additional charges apply based on order volume" language alone won't tell you the ceiling.

If you value the Built for Shopify badge and a strong rating, and want to start with static charts for free, SmartSize's Free or Growth plan is a reasonable starting point, moving to Pro 100 ($19/month, capped at 100 users/month) once you need the AI quiz. If you expect to clear 100 users a month quickly, check the higher-tier pricing on SmartSize's own site before you commit.

If every product on your store can share one identical size chart, none of this is worth paying for. Shopify's own metafield-plus-pop-up workflow is enough.

Takeaway

All three apps market themselves as "AI-powered size recommendation," but the plan at which that AI actually activates is completely different in each case. Comparing headline monthly prices alone will lead you to the wrong plan. Before you commit, confirm three things: which plan actually fits your product count and order volume, what the minimum plan is where the AI feature turns on, and whether there's a disclosed ceiling on overage charges as your orders or quiz usage grow.