Carat gets all the attention because it's the easiest number to compare. It's also the least useful one on its own — two diamonds of the same carat weight can look completely different depending on cut, and cut is the one thing most first-time buyers skip evaluating entirely.
Cut before carat
A well-cut diamond reflects light back through the top, which is what actually creates sparkle. A poorly cut stone can look duller and smaller than a well-cut diamond that weighs less. If you're choosing between a slightly bigger stone and a better-cut smaller one at the same price, the better cut usually wins on how it actually looks on the hand.
Certification is not optional
Ask for an IGI or GIA certificate for anything beyond a small accent stone. It documents the 4Cs (cut, colour, clarity, carat) independently of the seller, so you're not relying on their description alone. If a seller can't produce one, that's the question to push on before anything else.
Where it's fine to save
Clarity and colour grades near the top of the scale carry a real price premium for a difference that's often invisible to the naked eye. A diamond graded slightly lower on either scale, chosen carefully, can look identical in the setting for meaningfully less money — this is usually where a jeweller can help you get more stone for your budget without a visible trade-off.
The one thing to always check in person (or on video)
Photos and specs don't fully convey sparkle. If you're buying online, ask for a video of the stone under normal light before you commit — a seller confident in their stone will have no problem sending one.