The recommended intake of calcium per day varies a little with age:
As a rule of thumb, each dairy serving contains about 300 mg of calcium (8 ounces of milk, 1.5 ounces of cheese, 1 cup of ice cream, 1 cup of yogurt). The exception is cottage cheese, which has only has about 100-200 mg of calcium in an entire cup (though some cottage cheese is enriched with additional calcium; you will need to check the label).
There are many different types of calcium supplements. The TOTAL weight of the pill is listed on the label - which includes the compound to which the calcium is bound. This might be carbonate (the most common form - calcium carbonate is found in Tums as well as hundreds of other supplements), citrate, lactate or gluconate. The supplement should list the "elemental" calcium on the label - this is the ACTUAL dose of calcium in the tablet. For example, if you bought a bottle of Tums Ultra 1000, you would probably tell me that you are taking 1000 mg of calcium. This is not correct - you are taking 1000 mg of calcium carbonate, which contains 400 mg of calcium. To get to a dose of 1200 mg of calcium, you would need to take 3000 mg of calcium carbonate (3 pills), each containing 400 mg of calcium. Also, pay attention to "Serving Size" when the label tells you how much calcium you are getting. It may say you are getting 800 mg of calcium - listing the serving size as 2 tablets. READ LABELS carefully.
So, let's say you drink 1 glass of milk per day, plus have yogurt 3 days per week and cheese about 3 days per week. You wonder whether you should take a calcium supplement, and if so, how much. We can estimate that you are getting about 2 dairy servings per day, which is equal to 2 x 300 mg = 600 mg of calcium (roughly). You are over age 50, so you need 1200 mg of calcium per day. A typical calcium supplement that I recommend is calcium with D - which usually contains 600 mg of elemental calcium with 200 IU or 400 IU of vitamin D. In this example, you should take one of these per day, to get up to a calcium level of around 1200 mg per day. Now, if you take a mulitivitamin, you will want to check the label. Most multivitamins contain at most a 200 mg of calcium. If you add this to your supplements, you might be getting around 1400 mg of calcium per day (2 x 300 mg in diet, 1 x 600 mg in calcium pill and 1 x 200 mg in multivitamin = 1400 mg). This if OK.
Now, what about vitamin D? Studies find that upwards of 80% of people in New England have low vitamin D levels (due to lack of adequate sun exposure for much of the year). I recommend that most people try to get 1000 IU to 2000 IU of vitamin D per day. You do get a little vitamin D from your diet - milk has about 100 IU per glass. Many multivitamins have 400 to 1000 IU of vitamin D per day. If you don't take a multivitamin, I recommend that you take extra vitamin D in a dose of about 1000 IU. So long as you don't exceed 2000 IU per day, you should be fine. Vitamin D does improve muscle strength as well as bone strength, and has been found to reduce falls in the elderly.
Any weight-bearing exercise (like walking, jogging, treadmill, stair-stepper, general aerobics, dancing) will help keep your bones strong.