We use essential cookies to make this website and the calculator work. With your permission, we’d also like to use analytics cookies to help us understand how teachers use the site so we can improve it.
This website uses cookies and similar technologies. A cookie is a small text file stored on your device when you visit a website.
These cookies are required for the website to function and cannot be switched off in our systems. They are usually only set in response to actions made by you, such as logging in, securing payments or remembering certain site settings.
__stripe_mid, __stripe_sid) – used to prevent fraud and process secure payments.We use Google Analytics to collect anonymous statistics about how the site is used – for example which pages are visited and how long people spend on them. This helps us improve the calculator and content for teachers.
_ga – distinguishes individual visitors._ga_<property-id> – stores session information for a specific Analytics property.These cookies are only set if you choose to allow analytics cookies. You can change your decision at any time in the cookie preferences.
You can adjust your cookie preferences below. You can also delete cookies via your browser settings at any time.
You can control optional cookies here. Essential cookies are always on.
Required for security, payments and basic site functionality.
Help us understand how teachers use the site so we can improve it.