About Measurements: Measurements in my recipes are all U.S. standard (at least so far). There are charts available on the web that convert U.S., Imperial, and metric measures. The Imperial measures often use the same terms for different amounts. The difference between teaspoons is small, usually negligible for a recipe, but the difference is greater for a tablespoon, and even more so when using two tablespoons, and greater still between Imperial and U.S. quarts, so the measures are not precisely interchangeable.
The site “Total France.com” has a conversion calculator for U.S., Imperial, and metric measures, including volume measures, however, the smallest Imperial and U.S. volume measure the site converts is an ounce (a U.S. ounce is larger than an Imperial ounce). It is a somewhat useful site.
For an explanation of the differences and a handy chart, take a look at English Weights and Measures. I found some of the information here less than complete, but it’s a decent basic reference.
How to use conversions in these recipes: In the sponge portion of the recipe for spelt bread, for example, one cup of water is approximately 475 ml. One cup of flour is approximately 125 g. (Bread flour weighs a bit more than all-purpose flour, and whole wheat weighs less, so conversion becomes complicated!) One-quarter teaspoon of yeast, U.S. measure, is about 1.25 ml (a volume measure, not a weight measure, as I think would be standard with metric measures of yeast), and it’s not quite a quarter Imperial teaspoon (about .2 Imperial teaspoon)—though for this recipe, one could substitute a one-quarter Imperial teaspoon of yeast for a one-quarter U.S. teaspoon without making much difference to the outcome of the recipe.
There’s another pretty good converter over on “whatscookingamerica.net,” and it has charts for most measurements you can think of, including a “dash” and a “pinch,” although it’s difficult to tell whether a U.S. pint, for example, and an Imperial pint is being referenced, and the two are quite different.
Perhaps the most useful converter for bread bakers, however, is over at traditionaloven.com. It has a calculator for converting all-purpose flour, plain flour, flour-type 00, self-raising flour, rye flour, wholemeal and whole grains flour types, and conversions from weight and dry volume scales for baking recipes. (Description from the traditionaloven site.) The site has many other converters available, as well as a lot of great tips for baking — and even instructions for making your own wood-burning oven!
I also recommend metric-conversions.org, which has a very handy calculator to convert U.S. cups to metric.