Convert seed based measurements to pre-ground?

Converting whole spices to ground spices is not as simple as matching up the weights. Ground spices have a distinctly different flavour from the whole. The freshness of the grind will also affect the taste quite considerably as well as how carefully they have been stored. When the spice is freshly ground it will have a very strong intense flavour, so you would reduce the amount you use slightly. However, ground spices rapidly loose parts of their flavour. The taste changes and you may find you will end up using more than the recipe states in order to get a similar taste. However, you'll never get exactly the same taste, grinding changes the spice.

The best solution is to try to get an supply of the whole spice from an online store. You can then use them whole or grind them yourself, fresh, as the need arises.

Here's a really nice table: Culinary conversion calculators. It has quite a list of spices. Note that, as previously mentioned, you need to compare the weight of the whole and ground spices.

Also, freshly ground spices are a gazillion times more flavourful than spice purchased already ground!

See link to Chef's Resources for up-to-date information. To protect against link rot, the current state of the table (with lines w/out values removed) is below:

Spices Oz per Cup Tbl per Oz tsp per Oz ------------------------ --------- ---------- ---------- Ajwain 2.40 6.67 20 Allspice, Ground 3.37 4.75 14.33 Anise, Ground 4 12 Anise Seeds 3.56 4.50 13.5 Annato Powder (Achiote) 5.19 3.10 9.25 Basil, Ground 2.67 6 18 Bay Leaves 1.33 36/oz Bay Leaves, Ground 3.79 4.20 12.66 Caraway, Ground 5 15 Caraway Seed 4.10 3.90 11.70 Cardamom, Ground 3.31 4.80 14.50 Cayenne 3.56 4.50 13.50 Celery Salt 8.42 1.90 5.70 Celery Seed 3.81 4.20 12.60 Celery Seed, Ground 4.00 4.00 12.00 Chervil Leaves 1.12 14.33 43.00 Chili Flakes, Red 2.82 5.67 17.00 Chili Pods, Casabel 9/oz Chili Pods, Arbol 50/oz Chili Pods, Guajullo 5/oz Chili Pods, Japones 80/oz Chili Pods, Morita 9/oz Chili Pods, Pasilla 2/oz Chili Pods, Paquin 500/oz Chili Powder 3.76 4.25 12.75 Chinese 5 Spice 3.76 4.25 12.75 Chives 34 46.67 140 Cinnamon 4.09 3.92 11.75 Cloves, Ground 3.69 4.33 13 Cloves, Whole 3.00 5.33 16 Coffee, Espresso Grind 2.82 5.67 17 Coriander, Ground 3.35 4.78 14.33 Coriander Seeds 2.29 7 21 Cream of Tartar 6.40 2.50 7.50 Cumin, Ground 3.38 4.73 14.20 Cumin Seeds 3.84 4.17 12.50 Curry Powder 3.62 4.42 13.25 Dextrose, Powdered 3 9 Dill Seed 3.69 4.33 13 Dill Weed 1.70 9.42 28.25 Epazote 1.60 10 30 Fennel, Ground 3.72 4.30 12.90 Fennel Seed 3.69 4.33 13 Fenugreek Seed 6.19 2.58 7.75 Fermento 4 12 Flour, AP 4.25 Garlic, Granulated 5.65 2.83 8.50 Garlic Powder 4.49 3.57 10.70 Garlic Salt 8 2 6 Ginger 3.25 4.92 14.75 Herbs du Provence 1.45 11 33 Hibiscus Flowers 40/oz Kosher Salt 6.02 2.66 8 Lavender, Dry 1.07 15 45 Mace 3.24 4.93 14.80 Marjoram 1.41 11.33 34 Mint Leaves .53 30 90 MSG 6.40 2.50 7.50 Mustard Ground 3.43 4.67 14 Mustard Seeds 6.40 2.50 7.50 Nutmeg 3.87 4.13 12.40 Onion Powder 3.75 4.27 12.80 Orange Peel 4 4 12 Oregano Leaves 1.71 9.33 28 Paprika 3.84 4.17 12.50 Parsley Flakes .69 23.33 70 Pepper, Black Coarse 3.84 4.17 12.50 Pepper, Black Cracked 4 4 12 Pepper, Black Table Grind 4 4 12 Pepper Flakes, Red Crushed 2.82 5.67 17 Pepper, Szechwan 2 8 24 Pepper, White Ground 4.12 3.88 11.50 Peppercorns, Black 4.57 3.50 10.50 Peppercorns, Pink 7.50 Peppercorns, White 4 4 12 Pickling Spice 5.33 3 9 Poppy Seed 4.80 3.33 10 Pumpkin Spice 3 5.33 16 Rosemary, Ground 2.82 5.67 17 Rosemary Leaves 1.78 9 27 Saffron 1.20 13.33 40 Sage, Ground 1.45 11 33 Salt, Kosher (Diamond Crystal) 4.80 3.33 10 Salt, Kosher (Morton) 8.73 1.83 5.50 Salt, Seasoning (Johnny’s) 8.21 1.95 5.85 Salt, Table 10.13 1.58 4.74 Savory Leaves 2.67 6 18 Sesame Seeds, White 4.37 3.66 11 Sugar, Granulated 6.86 2.33 7 Sugar, Brown 1.5 4.5 Sugar, Granulated 1.5 4.5 Tarragon Leaves 1.30 12.33 37 Thyme, Ground 3.75 11.25 Thyme Leaves 2.29 7 21 Turmeric 4 4 12 Wasabi Powder 2.70 5.75 17.25

More info: http://www.chefs-resources.com/culinary-conversions-calculators-and-capacities/dry-spice-yields/#ixzz4lE9vGNSg

The right way to do this, of course, is by weight. So if you are willing to do the research to figure out how much 1 teaspoon of fennel seeds weighs, and you have a precise enough scale, you can just weigh out the same amount of ground spices. Failing that, I'd use about 20% less to account for the fact that ground spices are more densely packed than the seeds. (I just confirmed this for cumin - a teaspoon of whole seeds weighs 1.95 grams and a teaspoon of ground weighs 2.5 grams). On the other hand, if you figure that maybe the ground spices aren't as fresh and pungent, you might want to use the whole amount to somewhat counteract that.

For leafy herbs (which you didn't ask about), the typical suggestion is use half as much.

Try this link. I also have a lot of dried spices and not much access to the fresh ones.

http://www.smithandtruslow.com/spice_conversions.php