Density in a formulated syrup, where you choose the number

The ratio is the product

A syrup made from equal weights of sugar and water is about 50 percent solids. Two parts sugar to one of water is about 67. Those are weights rather than volumes, because a cup of sugar varies with how it was packed and a gram does not. Write the formulation in weights from the first batch, not after somebody else has to make it.

Why a thin syrup is a short-life product

At around half sugar the water activity is nowhere near low enough to stop spoilage, so a simple syrup at that strength keeps for days refrigerated rather than months on a shelf. That is a perfectly good product and it is a refrigerated one, with the shorter life and narrower route to market that implies. Many makers discover this after printing a best-before date that assumed otherwise.

Verify the arithmetic with the instrument anyway

Water evaporates while sugar dissolves, especially if you heat it, so the finished concentration is usually a little above what you weighed out. For a product you are putting a shelf life on, confirm the number rather than calculating it, and record what you confirmed.

What flavoring does to it

Fruit, juice and infusions bring water with them and dilute the syrup, which moves the concentration after you thought it was settled. A fruit syrup also brings acid, which changes the keeping question again. Measure the finished product rather than the base.

No identity standard, no external check

Nothing in the regulations tells you a bar syrup is too thin. The floor that a maple producer is handed is one you have to set, and the only way to know you are holding it is to measure every batch.

References