Subscription models work for daily users; top-ups work for occasional ones — but only if you read what the top-up actually buys. This guide compares the five AI tutoring pricing models UK families meet, and the one question that decides between them: is the thing you are buying time, or turns?

Updated 12 August 2026: the worked examples below used to assume a £14 top-up bought unlimited sessions for a month. It does not — ours buys 100 turns within 30 days — and the per-session figures have been rebuilt on the real unit.

The four models

Model Examples Typical UK price Best for
Subscription (flat) Khanmigo ($4/mo, US only); CENTURY home plans (from £8.33/mo annually) £8–25/month Daily or near-daily users
Metered top-up aitutors.me Extra Time (£14 for 100 turns / 30 days), some boutique services £2–14/top-up A burst of use, on a clock
Term-based / coach-led aitutors.me PRO (£360/term) Per term Structured, coach-supported study
Freemium Khan Academy + Khanmigo, ChatGPT-style, aitutors.me free demo £0 base, paid upgrade Trial-then-decide
School-funded CENTURY Tech, Sparx £0 to family School-provided users

Subscription: when it makes sense

The maths, and the unit that ruins it

A flat monthly subscription is priced in time: pay £14, use it as much as you like for a month. A top-up is usually priced in turns: pay £14, get a fixed number of exchanges, often on an expiry clock. The two look identical on a pricing page and behave completely differently.

For a genuinely unlimited £14/month subscription:

Sessions/month Cost per session
4 £3.50
8 £1.75
16 £0.88
30 £0.47

Below about six sessions a month you are overpaying; above eight, a flat subscription beats anything metered.

For a metered top-up, the maths stops at the meter. Our own Extra Time is £14 for 100 additional demo turns that expire after 30 days. If a session is ten back-and-forths, that is roughly ten sessions — about £1.40 each — and the thirty-first session does not exist at any price. Per-session cost never falls below that floor, which is exactly why a top-up is a burst, not a habit.

Before you buy any top-up, ask what one unit is. A turn, a session, a month, a question — the word is doing all the work.

When subscription wins:

  • Your child uses the tutor 3+ times per week
  • You're trying to build a daily 20-minute habit
  • You don't want booking friction
  • You expect 12+ months of consistent use

When subscription doesn't make sense:

  • Pre-exam crunch only (use freemium for the month)
  • Your child uses it sporadically
  • You're not sure if they'll engage long-term
  • One-off subject difficulty (e.g. "I just need help with Year 8 ratio")

Pay-per-session: when it makes sense

When it wins:

  • You expect <6 sessions/month
  • Specific topics, not general practice
  • One-off "stuck on this homework" use
  • You're hesitant to commit to a subscription

When it doesn't:

  • Daily use (much more expensive)
  • Habit-building goals (friction kills the habit)
  • Multiple topics over multiple weeks

Freemium: the gateway

Khan Academy + Khanmigo's free tier is a legitimate option. The free tier covers most KS3 maths topics adequately. The paid Khanmigo subscription unlocks the AI tutor on top.

Best move: start free for 2 weeks. If your child engages, decide whether the paid tier or another subscription (aitutors.me, MedlyAI) fits better.

School-funded: the unbeatable price

If your school provides CENTURY Tech or Sparx Maths, your child gets a real AI-powered tool at £0 cost to the family. The downside: not chosen by you, and may not match your child's learning style.

The smart move: use the school-funded tool first. Add a subscription only if there's a gap (most commonly: Sparx doesn't tutor — see aitutors.me vs Sparx Maths).

The trial period rule

Any subscription you can't try free for 7–14 days is one you should be sceptical of. AI tutoring is impossible to evaluate from a marketing page — only your child's actual engagement tells you.

aitutors.me offers a free live demo (no card, no signup), and Khanmigo and most reputable services offer trials. Use them.

The annual upsell trap (and the genuine annual deal)

Some services offer "annual = 2 months free". This is real value if:

  • You've already used the monthly plan for ≥3 months
  • Engagement is consistent
  • You expect at least 12 more months of use

It's not value if:

  • You're at month 1 of a trial
  • You're not sure your child will stick with it
  • You haven't checked the cancellation policy

Rule: never sign annual on a free trial. Run monthly for 2–3 months, then decide.

How aitutors.me thinks about pricing

(Disclosure: I run aitutors.me. This is the pricing rationale.)

  • Free live demo — a real Socratic tutor you can try in the browser, no card and no signup. Evaluation should cost nothing.
  • Extra Time (£14 one-time, 100 turns, 30-day expiry) for a burst of practice — a metered top-up, not a recurring subscription, so there is nothing to cancel and nothing that renews behind your back. It is also capped on purpose: it is for finishing an evaluation, not for replacing tuition.
  • PRO (£360/term per subject) for coach-led tuition: a named human coach plus the full professor faculty, for families who want structure.
  • Max and Team for weekly 1:1 and schools. Full current tiers live at /pricing.

Many subscription tutors over-charge at MVP because they need runway. The move I prefer is to let families evaluate for free, keep the entry top-up small, and reserve the higher price for the coach-led product where a human is genuinely in the loop.

Decision framework

How many sessions/week do you expect?
├─ 0–1: pay-per-session or freemium
├─ 2–3: freemium first, then subscription if engagement holds
├─ 4–6: subscription (any reasonable one)
└─ 7+: subscription only — pay-per-session is uneconomic

Does your school provide a free AI tutor?
├─ Yes: start there. Add only if there's a gap.
└─ No: start with a free demo, then a top-up or subscription

FAQ

Is a subscription AI tutor better value than a top-up?

For daily users, yes — break-even against a £14 unlimited subscription is around six to eight sessions a month. But check whether the "subscription" is metered: if it caps turns, the comparison is not time against time and the per-session floor never drops.

Are AI tutor subscriptions worth it?

For habit-formers, yes, provided the plan is genuinely unlimited. Daily twenty-minute sessions for a flat £14 a month works out under £0.50 a session. On a metered top-up the same usage runs out partway through the month.

What's the cheapest AI tutoring option in the UK?

Free if your school provides it (CENTURY, Sparx). Otherwise CENTURY's own home-learning plans, from £8.33 a month on an annual plan. Khanmigo is cheaper still at $4 a month, but Khan Academy requires US residence and a US billing address, so UK families cannot buy it.

Written by Duke Harewood at aitutors.me. Updated 20 May 2026.