Is Tofu (Firm) Safe for Kidney Stones? (Safe)
mg oxalate
per serving
Serving: 1/2 cup (126 g)
Verdict: 🟢 Safe
Per 100g: 1.6 mg
Data: Harvard T.H. Chan SPH (2024)
What this means: Tofu (Firm) is rated Safe (🟢). At 2 mg oxalate per serving, it's well under the 25 mg safety threshold. You can include it regularly in a kidney stone diet. Pair it with calcium-rich foods (dairy, fortified plant milks) for additional protection, and drink plenty of water throughout the day.
Among legumes, Tofu (Firm) sits well below the category average of 20 mg. For context, 44 out of 60 legumes (73%) are rated 🟢 Safe (under 25 mg oxalate/serving). The average legumes in our database has 20 mg oxalate per serving — which means Tofu (Firm) is 90% below the category norm. Within its specific category, Tofu (Firm) ranks among the lower-oxalate options. This context matters because two 'Safe' foods can have very different oxalate levels — one might have 5 mg while another has 24 mg. Both are Safe, but the first gives you more dietary flexibility. Browse all legumes rated Safe to compare within the same verdict level.
Why does the safe threshold matter?
The 25 mg line is the reference point clinicians use to separate everyday foods from ones that need caution. Every value on this page traces back to Harvard's 2024 lab analysis, so the threshold is applied to measured data rather than estimates. Tofu (Firm) comes in at 2 mg oxalate per 1/2 cup (Safe) in the measured database.
Can I eat this food every day?
If it's in the Safe zone (under 25 mg/serving), yes — it can be a regular part of your diet. For Caution or Avoid foods, frequency matters. Rotate them with lower-oxalate options throughout the week. For context, Tofu (Firm) measures 2 mg per 1/2 cup, rated Safe.
Where does the oxalate data come from?
The numbers come from Harvard T.H. Chan SPH's 2024 laboratory measurements, published through the OHF database. Direct lab analysis, which is why they're treated as the reference values for food oxalate. For context, Tofu (Firm) measures 2 mg per 1/2 cup, rated Safe.
Should I also check sodium and calcium?
Definitely. Oxalate is only part of the story — high sodium raises calcium in urine, and dietary calcium (from food, not pills) binds oxalate in the gut. The food's main page lists both, so it's worth checking before you plan around it. For Tofu (Firm), the measured oxalate value is 2 mg per 1/2 cup (Safe).