Concrete PSI Calculator
This concrete psi calculator does two jobs: converts compressive strength between psi and MPa (with the matching M-grade), and estimates strength at any age using the standard ACI maturity curve — how strong is my slab at 7 days?
Come usare questa calcolatrice
- Inserisci le tue dimensioni — piedi per le lunghezze, pollici per lo spessore.
- Regola le opzioni — percentuale di sfrido, dimensione del sacco e il prezzo locale del calcestruzzo.
- Leggi i risultati — volume, sacchi, peso e costo si aggiornano in tempo reale mentre digiti.
La formula
MPa = psi × 0.006895. Strength at age t (days): f(t) = f28 × t ÷ (4 + 0.85t) — ACI 209 type curve Esempio svolto: A 4,000 psi (27.6 MPa) mix at 7 days: 4000 × 7 ÷ (4 + 5.95) ≈ 2,814 psi — about 70% of design strength.
PSI is the US strength language; MPa (and M-grades) the metric one. Anchors: 2,500 psi ≈ 17 MPa, 2,900 psi ≈ M20, 3,600 psi ≈ M25, 4,350 psi ≈ M30, 5,000 psi ≈ M35.
Choosing psi by application: 2,500–3,000 psi for footings and walks, 3,500–4,000 psi for slabs and driveways (4,000+ with air entrainment in freeze-thaw climates), 4,500–5,000+ psi for structural and commercial work.
Strength grows fast then slows: roughly 50% at 3 days, 70% at 7 days, 90% at 14 days, 100% of design at 28 days — the concrete calculator psi curve above assumes moist curing at normal temperatures; cold weather slows everything.
Domande frequenti
Domande comuni sulla concrete psi calculator.
What psi concrete do I need?
Footings/paths 2,500–3,000 psi; slabs and driveways 3,500–4,000 psi; structural or commercial 4,500+. Freeze-thaw exposure: 4,000 psi minimum with air entrainment.
How do I convert psi to MPa?
Multiply by 0.006895. 4,000 psi ≈ 27.6 MPa. Reverse: MPa × 145 = psi.
When can I drive on new concrete?
Light vehicles after 7 days (≈70% strength); heavy vehicles after 28 days. Foot traffic is fine at 24–48 hours.
Does concrete keep getting stronger after 28 days?
Yes, slowly — given moisture, it can gain another 10–20% over months. 28 days is the design/testing benchmark, not the end of hydration.
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