Questions & Answers about Das Budget war erheblich kleiner, als wir kalkulierten.
Why is the verb kalkulierten at the very end of the sentence?
In this sentence, als acts as a subordinating conjunction introducing a full comparative clause ("than we calculated"). Just like with dass or weil, this kicks the conjugated verb—in this case, kalkulierten—to the end of its clause.
Could I use wie instead of als for "than" in this sentence?
No, because this is an unequal comparison. Since the budget was smaller (kleiner), you must use als. You only use wie for equal comparisons (e.g., so klein wie, meaning "as small as"). Even though you might hear native speakers mix them up in regional dialects, standard German strictly requires als here.
Is erheblich the most common word for "considerably"?
erheblich is an excellent, slightly formal B2-level word for "considerably," "significantly," or "substantially." It fits perfectly here in a business or planning context. In a casual conversation, you might simply hear viel (much) or deutlich (clearly) used in its place.
Could I say als wir kalkuliert haben instead of als wir kalkulierten?