I also wanted to note, the phase-out range is different depending on your marital status and whether each of you has a retirement plan at work. It is calculated for each individual, not for a couple, and the members of a couple can have different situations.
For example, I have a retirement plan at work but my stay-at-home-dad husband does not. So the phaseout limit for him for a tIRA is much higher than for me ($183000-193000 is the phaseout range for him).
Also for a married couple, if one of you is eligible to contribute, the other one is as well, even if one doesn't have earned income or doesn't make $5500. My husband makes $20 a week at a part-time job, but we can still contribute for him, and could even if his income was 0. Our income puts us right in the middle of the phase-out range for me, so we funded his first and for mine will fund whatever amount ends up being deductible.
Alternately we could fund my IRA and recharacterize anything that didn't end up being deductible as Roth. We don't have the extra $ to do that but it's a viable option for others in this situation.